What does fdev do? The extend the progression. And yes, it was limited...to start with. Until everyone complained.
Now, the things required for engineering can be found in many, many different ways. And on top of that, they later added materials traders, precisely because players hated the kind of gameplay you're trying to create. Now, you can get any engineering currency doing almost anything in the game. Exactly like credits.
Converting currency is a symptom of a different problem. Limited gameplay. Not a symptom of the currency being isolated. Players have no option in a given game loop but the base level grind. So they have to either suffer thru something boring at usually tedious rate or not partake at all. There is no game loop that actually requires a test of skill built over it that would allow a player to get good at something to skip the grind and accomplish something in less real time but maybe at a higher level of effort on their part. So currency conversion is a bandaid because it's easier to do that than implement decent game mechanics.
but even that is better than the single currency system. because you control the conversion rate and so maintaining balance between various roles is done easily here without impacting the local use of the individual currencies in whatever balance was set for them.
If i'm say, exploring and getting some kind of reward that is associated with exploration that I accrue, rather than this reward being an impact to the bgs/game, then that reward can be balanced in a way that is balanced to the costs of me exploring. compensating my activity fairly. If i then shift to something like bounty hunting or merc stuff etc, i get some kind of bounty hunting/merc reward. Now if i want to convert remaining exploration rewards to something usable in bounty hunting, a conversion (trader) could be visited that would convert them. but the conversion rate would maintain the balance based on how the developers feel each activity compares in difficulty to acquire. Simple. intuitive. No need to have this arms race of reward buff cycling that we have now.
Don't get me wrong! I see what you're after! It's just that most players don't care. They just want their 'credits' - or whatever other currency lets them achieve progress - and no questions asked. It doesn't matter how you craft it, how carefully or elegantly you conceal it, players will complain, and whine, and quit, until the devs give in and change it right back into a credit variant once again.
That's a problem that is created because the gameplay is not something players enjoy in of itself. It's something they loath. so they look for ways to reduce having to do it. It's an odd behavior to have in a game that you aren't being forced to play but it's just psychology. Some people want to like elite, and people generally get addicted to getting stuff. Even if that stuff is pointless. But the gameplay is basic and quickly becomes repetitive and boring. So players demand to keep getting that fix of winning but without having to continue doing what they were doing as much. Since there are no game play loops beyond what they are already doing they demand either nerfs to the time sinks (FSD jump range extensions, mission stacking, predictable markets, mining hotspot overlaps, etc) or buffs to the rewards (credit reverse inflation).
We're (and we've been) at the point where credits are acquired so quickly to such a huge amount by players that it really only punishes new players for credits to exist at all. They are meaningless to anyone else having played more than a month at most. Rather than buff the credits in yet another role that will just cause more buffs to credits in other roles after and continue this endless cycle, it would make more sense to just eliminate credits. Even if you dont replace credits with another currency, it would be better than the continued waste of time credits cause the developers in trying to maintain balance. They could place certain things behind achievements from activities or reaching certain triggers if they didn't want to adopt the method most other games have come to find as the best option. I would easily see and accept a total elimination of credits before continuing to use credits to buff compensation as a means of trying to cover up boring gameplay grind loops.
Nobody is not doing xeno biology because it doesn't pay a lot. They're not doing it because all things being equal, other things may be paying more or because they realize it's really pointless and lacking actual gameplay and dont want to play it. All making it pay more could do is exactly what you described you dont want to do, force players to feel like they have to in order to make the best profit. Because if it's not buffed enough, there will be no impact to player participation, the same people already choosing to play it will be the ones playing it after. If you want xeno biology to be rewarding enough to draw players or even feel rewarded yourself, the real solution here is to actually have something worthwhile to do in the role and make the game actually care that you're doing it. Then credits become a distant second or third consideration, like it should be since nobody is hurting for credits.
Also, trading absolutely has skill. There are plenty of players who don't bother to pursue it, but then, there are plenty of players who just equip gimballed multicannons and beams on a corvette and rack up billions in bounties, too. That doesn't mean doing so is the limit of skill in pve combat. I wish you'd stop trying to denigrate the aspects of the game you see as 'lesser' - especially since it seems you consider about 90% of the game to be that way.
you're trying to paint exploration as dangerous and requiring skill when it only requires staying awake and having a lot of time available to watch loading screens and look at things that dont respond to you. I'm not denigrating anything, i'm actually observing it for what it is and you're trying to romanticize activities that players do when they first learn how to play the game and then that's all they do ever after. Trade is safe, There is no risk there. exploration is safe, there is no risk there either. That's why players can do it and rack up millions and billions of credits repeating the same game loops and never die. Not the best players, almost all players easily and quickly make more credits than the game costs can support. The only difference between them is how fast they want to complete the repetitions before that either burns them out or they feel like doing something for some reason other than rewards. PVE combat is in the same boat, but pve combat is one of the few places where there exists a way to actually scale skill despite the limited activities because it's one of the few things that allow the game to alter the difficulty of an activity to the player. It's not leveraged well, but it's an order of magnitude beyond the progression scale of the other roles. PVE combat is safe because it's predictable and entirely optional - you can easily choose who to fight and when so you're never faced with a situation that you'll lose unless you want to be. So while there is a bit of skill to combat, there is no risk despite the rewards being balanced as if there were.
That's not just my opinion, that's why players whine about buffing all of the various things these game loops have in place as a "cost" to players. Because there is no progression of skill in the gameloops so what was at the beginning a fair cost, is now a tedious annoyance - but with a single currency and a single game loop, you can't improve the situation for one level of player without impacting all of them. So now players spend a few dozen hours playing and now have enough credits to buy everything in the game. You have costs that are still at launch levels and pointlessly low for some things and new items that are at costs that dont make any sense when compared to the costs of older things (foot costs vs ship costs).
Trading does not have skill. Trading is just about who can repeat the same actions over and over again after looking up whatever the market has said is worth the most that has the shortest travel distance online that everyone else hasn't already started doing.
This is why it's the goto for newbis to make credits, because it's the safest activity to get the most credits in your time playing. Not because it's full of risk and requires so much skill.
likewise with mining, if they were dangerous ...hard things to do requiring skill, it wouldn't be the thing everyone tells new players to do as soon as they can to eliminate having to care about credits. This romanticized version of the game you have is amusing, but just doesn't mesh with reality.
Lastly, everything is a race. That's basically what skill is. If one player kills a hydra in 5 minutes and another takes an hour, which is more skilled? If one player clears a conflict zone in 10 minutes and the other in 20, which is more skilled?
No, that's the only thing the game has in most roles to delineate player experience because in a grind loop all you have is how fast you can do the grind loop so you can do it again. You speed run the game loop because you dont care about the game loop's content ..because you've seen it before and it never changes and doesn't matter. And since you're in the grind loop for the reward, you just go after the reward. Even if you dont need it.
most players who dont quit the game for various reasons will gather their credits in the various easy money ways and then they do the things they want to do not caring about credits and speed running the game loops to repeat it as fast as possible. The game loops dont require skill. Skill is not speed running. Because credits dont matter soon after playing. you have plenty. And speed running the only content in the game doesn't make sense. But some players with more addictive personalities will continue anyway or maybe they just got tired of what the game has and made their own goal of finding out how fast they can do a certain thing.
The point is, a skilled game loop allows you to master an activity doing a more difficult task that tends to also impart a higher risk with a reward that scales either how well you succeeded or by succeeding at all. Completing any task slower or faster, might be something that requires skill or it might be something that just requires not caring about playing - it really depends on the task. If i can beat a level in mario faster than everyone else, that can be seen as a skill but it's at the expense of all of the content in the level that i'm skipping to do so and I'm getting none in return because i've converted the game into a race instead of what it was designed to be. That's what completing grind loops faster is. Depending on the task at hand, it could require being more skilled to accomplish and some players couldn't do it (like clearing cz's). but doing the only activity available faster and having that be what you actually care about is a symptom of a problem in game design than what you should be striving towards. You shouldn't want to cram as many repetitions of the same action into as little time as possible. That's not what is meant by having a skilled game mechanic or roles requiring skills. That's just players finding the most efficient way to not play the game to get at your reward or having given up on whatever the point of the game was and making their own personal objectives.
Proper skilled gameplay is that which you aren't able to do from the start of the game or if you can, you're not reliably successful. You have to learn how to do a certain task or beat a certain kind of opponent or solve a certain kind of puzzle. And a mechanic has risk when attempting a task, even slowly has a non-zero chance of failing even if you dont want to fail. Anything players do to make crazy money is easily provable at not having either. Something with risk or requiring skill to do would not be something grindable and reliable for even newbies to accomplish. And setting a game up so your players are always looking for the best way to not really play or appreciate what's going on because they're too busy speed running is not how you want your game to be played. It just tells you that it's not the game they want to experience, just a means to an end.