Lets see, most of what I would have said has been said.
1. I'm going to echo what Zoe.Sakura has said: Roleplay what you want to roleplay. If you want to RP a policeman, do it. A trader? Awesome, go for it. A pirate, good luck, hope to see you!
The reason RP in disco works and the balance between types of people stays relatively the way it is is because it's designed that way. Trade = the lifeline of Discovery.
2. The problem is this weird need from everyone to make the most money, no matter the cost.
If you're playing a police character to get money, you've entirely the wrong outlook on how things work. Of COURSE a policeman gets paid, damn well too. We could all use a little imagination and pret...roleplay that you DID get paid when you transfer money from your trading character?
3. It all seems to me, a matter of immediate results - when you get pirated, chances are you get some form of RP out of it. Where is your in-game RP when you are paying taxes? Transferring credits to a bank character at the end of each run/login? You don't know how many times I've RPed with a trader as a police character, the same amount that I would with any of my pirate characters and yet, does the trader think about "donating" or "tipping" to the police for his good work? Rarely. It usually winds up being official factions that do anyway. (So in a strange way - your system is almost already in place.)
Bottom line, do to others what you would want done to you. Give them a wonderfully played out roleplay and you may get the same, and some credits to boot.