I've been watching this thread since its inception and I'd like to put my two cents in by saying the following:
I absolutely agree with the OP in almost every way - Criminal game play should be a legitimate way to "enjoy" the game with criminal specific (and of course, legal specific) exclusive content. Players should be allowed the ability to flip flop between these styles of play (a rogue who decides to go straight, or law abiding citizen who goes dark), and not by flipping a switch between "pirate mode" and "trade mode". Your actions should indicate your career, and the more actions you take towards a specific cause, the better you will be known among people as an advocate of that cause.
The only point of potential disagreement I would have with the OP is the notion of "high reward". Not that I disagree that it should be high reward - it definitely must be high reward - I just don't want those rewards to be limited to credits. Any type of credit-bound game play will get stale when people have billions to splurge. We need to give more depth.
I feel we can't really discuss this without going a bit into the PVP component of the game. A long time ago, I proposed a "fix" for the crime system in the game, because in my opinion, all "mindless pvp" as I like to call it stems from a sense of boredom and a desire for more action packed game play. It is due to this fact that people kill without mercy, just for laughs. Most "PvPers" aren't interested in fair fights of equal skill and instead opt to ambush or gank people who are easy prey.
The proposal I outlined on these forums that I refer to was to fix the entire pyramid of PvP (as I saw it, at least) from the ground up. This meant you needed to enhance trade first (to better populate Open), which would then feed into enhanced piracy, which would ultimately feed into enhanced bounty hunting.
This might not seem so connected to some of the readers of this post, but please stay with me for a little while longer. My idea is as follows:
Every "profession" gets a dedicated progress bar for the various types of game play that you can have in Elite. The Pilot's Federation is the governing body of these professions, and they essentially work as ranks within ranks split between trading, exploration and combat - Instead of giving you ranks as we know them, a higher progress bar gives you reputation among the people within that circle and the higher you go the more renowned you become as a professional of that type of game play. Some of these can be mutually exclusive for lore reasons like, for example, trade and piracy.
Allow me to get specific.
I picture the piracy progression bar to scale up by ton of stolen commodity. This breaks the idea of "useless" cargo being pirated, because 1 ton of fish is just as profitable as 1 ton of gold since we aren't linking it to credits, but rather to reputation among the piracy circles. If you steal a specific number of tonnage, you get access to pirate-specific perks. Decals, paint jobs, and more "black markets" to conduct your shady business. Eventually you unlock the Elite version of a centralized piracy hub. An asteroid base that nobody can find unless invited to. This base provides specific perks, similar to how Founders world works now.
You build a reputation as a great enough pirate, and that will land you on the boards of the bounty hunters...
For the bounty hunters, these guys abide by the law and increase their reputation by killing wanted individuals, NPCs or players. They get to work with the various law enforcement agencies of various systems and super powers to get bounty-hunter specific missions, with good pay outs and similar rewards to the piracy idea above. Most importantly, they get access to the "Hunters Board" which is a specialized version of the mission board system exclusive to the most notable bounty hunters in the galaxy. This board gives them mission spawns to assassinate the most notable pirates in the galaxy, for a huge bounty pay out. The mission gives clues as to the last known location of various pirate lords (who are actually players) and that data only updates when that pirate gets scanned. Emergent game play.
For trading, you can earn enough reputation that you get a notification when specific systems go into negative states (famine/outbreak, etc) like some sort of "help be Obi Wan Kenobi, you're my only hope" type message that offers massive payouts for these guys if they help those systems in a timely manner. This of course is also fed to the pirates, who target those systems more, which then feeds into the hunters, who go to preserve the peace.
For exploration, you can have different subsections of deep space explorers, with varying mission types between passenger missions, anomaly discovery, or material research. These guys essentially choose branches of exploration they enjoy, getting heads up messages about randomized derelict ships that lead to more discoveries and puzzles to solve, or a specific request to go map out a particular region of space.
The possibilities are almost endless. All factions get decals and paint jobs and other in game perks that allow them to fly the colors of their trade.
Crime and Punishment must be more heavily incorporated into the game to keep Elite relevant and open more possibilities. With that comes harsher punishment systems for people who just want to be murderers. It's perfectly acceptable game play, but the consequences are severe in game and not credit related at all. Things like stopping them from docking at all high/medium security large stations would be really cool. Feeding their data as murderers into the bounty board I mentioned earlier would also be super fun for both hunter and hunted.
All of this stems from the same core issue that the game has: We need more specific avenues of game play. Blazing our own path doesn't really mean much if all paths simply lead to more credits.