Sooner or later, you get in a position where credits don't mean much to you. Rebuy? I *might* get a rebuy screen if I'm goofing off in my unengineered trainer eagle. It hasn't happened yet, but it's possible. But that credit amount? Ha. If I'm rolling in one of my real ships- FAS, Anaconda, etc? NPCs are not going to take those ships down. They aren't good enough pilots and their weapon loadouts are laughable.
I've never done Quince (I don't care about Imp rep and I have hundreds of millions of credits just laying around). But I don't really think it's a gameplay advantage at the end of the day. That's because this game is not about buying the best ship. It's about being the best pilot. Buying the best ship can and does happen pretty early on. Being the best pilot is a never ending process.
The main failing of Elite, in my eyes, is that too many people mistake buying the most expensive ships as the endgame. It's not really Elite's fault. There are lots of games set up like this, because the skill ceiling is so low that the only way to "level up" is to get better gear. MMOs especially are guilty of this. But Elite is not an MMO style game. It's a flight simulator with some arcade elements added in and multiplayer.
THIS. THIS THIS THIS. Lets say I go to Quince, make ten billion, fully G5 engineer an FDL, then go and interdict Harry Potter. Guess what's gonna happen? HP is gonna blow me away with two arms tied behind his back. I like Quince and its sort because it makes SKILL, not money, the determining factor in a PVP engagement.