Edit note: if you read this as "I think the player should never die", "I think the game should be made even easier" or "I think the game should have lower risks for higher reward" you're reading it basically entirely backwards to my intent. If you could point out the bit(s) of the post that are leading to you that conclusion I might be able to reword them to be clearer.
Not to put too fine a point on it, your entire post is coming across as why players should never, ever die.
Many big problems with Elite Dangerous - it's multiplayer, it's in space, it has a finite budget, it's a bit like Elite - are also its key defining features and the reasons to play it so much. The inevitable compromises aren't great, but we want to play "multiplayer Elite" enough that we (mega-threads aside) usually accept them.
Well, speaking personally, I would not miss the 'multiplayer' part too much if Frontier announced tomorrow that they were patching out Open mode.
One big fixable problem, however, is that the game is designed so that the player is not supposed to die. We all know players are not supposed to die: "I did X and died" threads exist, and the response is "maybe you're incompetent" rather than "well, yeah".
Maybe because such threads are implying or outright stating that 'X shouldn't kill me', and the response is 'well, yeah, X shouldn't kill you - if you're competent at doing X. Maybe you're not.'
This causes problems for the game:
1) NPCs can't be made any tougher - and maybe still need nerfing - because if they are they might kill players, which is against the game design.
2) PvP, ending as it often does in a player death, is against the game design (outside of CQC, where players are supposed to die frequently and the game is designed around that)
Maybe this is where you need to express yourself clearer - player death (or as close as this game gets to it) is very much part of the game design. This game doesn't make it a proper permadeath by having an escape pod which ejects you when your ship is destroyed, allowing you to use insurance to claim your ship back, for a cost in credits, or respawn in the starting Sidewinder, but it is a 'death'. This simple fact negates these supposed problems.
When a player does die, the risk/cost is wrong. Traders and explorers have more vulnerable ships because their profession requires non-combat internals and lose more cash and progress if they die. A trader buying Palladium for 12.5k per tonne and selling for 14k, for every time they die, they need to make 9 successful trips to cover the lost cargo, plus a few more for the ship rebuy. To do better than break even, even a 5% death rate is tough.
Nope. Traders and explorers have good reasons for considering having non-combat internals, but there is nothing forcing them to do so. I can't speak for exploration, but my experience in trading is that you can easily turn a decent profit, even on occasions where I've run with no weapons to maximise jump distance and replaced my shield with another cargohold to maximise profit, leaving me even more vulnerable to ship destruction than a more sensible trader. Your Palladium example is actually not a good one, as that works out at, what, 12% profit, or thereabouts? A better one would be, say, Medical Diagnostic Equipment. You might have to fly a bit of a long route to do it, but you can buy those for about 2k per tonne and sell for about 7k per tonne, a 250% profit. More moderate length routes might restrict that to only a 100-150% profit. And that's leaving aside long-distance rare trading, which can get into really silly percentages of profit.
This is impossible to balance. You cannot make NPCs so specifically (not) dangerous to kill a trader only one trip in 20. They're either going to be no threat at all or kill traders so often that they can't turn a profit. For explorers it's even worse - NPCs can never kill an inbound explorer in a balanced way. We say "never fly without rebuy" - but explorers easily carry more exploration data than the ship cost new.
So, with explorers, you run a risk of losing a lot of valuable data by having your ship destroyed - but, if that doesn't happen, you get a huge payday. Seems balanced to me.
Finally, with the right (not obvious) tricks, you can quickly become a billionaire and not have to care about rebuys anyway.
If you know of an actual cheat or exploit, report it to Frontier. Otherwise, you are basically moaning about players succesfully making money in this game.
So it's a mess - the player is not supposed to die, but it really hurts if they do. The players least able to avoid death (traders, explorers, inexperienced) lose the most both proportionally and often absolutely on death, while combat players are at lower risk and lose less. The consequences of this spread out and cause a lot of the bitterest community debates.
It's called 'risk v reward'.
So, I can see three basic paths for improvement, all of which would include the removal of fast escape mechanisms such as submit-highwake. There are probably others, too!
1) Implement "lack of player death" properly.
Players aren't supposed to die - so players can't die. Anything which would cause fatal hull or module damage to a player has no effect. (Well, it would at least be consistent...)
I really hope this isn't a serious suggestion. It would utterly trivialise the game.
2) Remove penalties for death almost entirely.
Destroyed players return to their last station with their ship and all attached cargo, data, transactions, missions, etc. in the state they were in immediately prior to destruction. Pay for repair to damaged subsystems and hull as if you'd narrowly escaped instead, and pay fines as now, but that's all.
Piracy gets a bit harder since players have no incentive to give up cargo - if you kill them with it on board, they keep it, whereas if they give it up (or you steal it) they actually lose it - but without fast escape there's time to force cargo drops, and hatchbreakers can be buffed.
NPCs can now be made much tougher because they don't cause significant losses - even one successful trade trip will make enough profit to pay for a few full repairs. Similarly it's not a big deal if a player shoots you down - just get back out there and shoot back!
This "equalises upwards" the experience so that death has the same effective consequences for everyone as it does for the current ultra-rich.
Not really much different from suggestion 1.
3) Rebalance the professions so death costs are more similar in terms of "time to recover"
This one is complicated and I've left out the details because they'd need months of adjustment to get right. The aim is to allow players to be killed without making this prohibitively difficult to recover from - but keeping the current gameplay where it does have a cost which one would wish to avoid if possible.
General: combat-oriented equipment and ships have much higher rebuy %, non-combat have much lower rebuy %. Buff NPC numbers and skills enough that they can be a threat to anyone; use system security levels and an expanded player reputation system (reprisals) to allow players to find their own level for risk/reward.
Well, a much better law enforcement/security system is something that Frontier want to implement, but I don't see the issue with ship rebuy costs at all.
Trade: much better sell:buy ratios. Increase pirate threat significantly.
As I pointed out above, even without rare trading, you can get profits into triple-figure percentages if you know what you are doing. I don't really think that needs buffed. I do find it interesting, though, that you're saying pirate threat needs to be increased when the very supposed issue that you're complaining about above is the vulnerability of traders.
Exploration: introduce a network of UC comms relays every few kLY across the galaxy to allow periodic sale of data - avoid the all or nothing nature of exploration by being able to cash in every few million (like a trader or fighter can). Introduce more exploration hazards of various sorts.
I can kinda see why you'd want this, but there's a major problem. The whole point of exploration is going out into the black to areas where no-one has ever been before and discover what's there - so who dropped the comms relays?
Losing a non-combat ship should be less punishing in terms of successes-to-recover; losing a combat ship is worse than losing a non-combat ship (but still less likely). Players can largely avoid combat at the cost of profitability by sticking to high security systems and not taking on missions which actively harm opposed factions.
Billionaires will have a lot of enemies, so while making a billion might be "easy", keeping it can be made as hard as necessary for balance.
In contrast to '2' this is intended to "equalise downwards" so that death is a concern and possibility for everyone (and perhaps more so for the "endgame" players).
(This is my favourite option and so of course it's by far the hardest to implement)
Except the problem is, if you do this, you're basically punishing success.