The problem with your "uber mining area" idea is that if it really generates a ridiculous amount of credits, tons of people will go there. Some people will go out of the ZOI and RP in order to get the huge profits. A large concentration of the server's population could be focused on just one area - which is not really ideal.
I think that mining should eventually overtake trading as the number of miners/transports increase. Smuggling should be a little bit more profitable than trading (just a little bit, as traders get pirated more than smugglers get fined).
Missions should give enough credits just to sustain a character, instead of being able to fund more (unless you do tons of high-yield ones). Alternatively, the repair and ammo costs could be reduced by a certain level, so fighter characters wouldn't need to drawcash so often.
Edit: one thing I'd like to see changed about the mission system is the levels of difficulty. It's impossible to fund an LPI character for instance through missioning, as the rewards are crap in the low-level liberty area. Perhaps a few special missions could be added on certain bases to allow characters in the houses to make back ammo/repair costs.