Some form of credit transfer between players, which is a strange omission in a game where trading has a strong focus.
With it you could have;
Inter player trading
Protection money
Player set bounties.
All that depth from a simple addition.
Yeah, we need people spamming comms and forums with Jita scam spam.
"Quitting Elite! Pay me 50.000 credits and I will send you 500.000!"