I find it's often pretty easy to get out of jail just by requesting a Trial by Jury. I think I get out about 80% of the time by doing this. Perhaps tack on a 10% fee (based on your bounty) for the court fees (scheduling, paperwork, paying the jury, etc) when you request trial. This fee could be for all requests or applied if you are found guilty. It's just another thing someone would consider before paying a ticket, choosing jail, or requesting a trial.
With regard to the lack of Cop RP... while I find there are a number of cops that won't listen to any RP there are a lot of us out there that would prefer to RP a scenario regardless of the size of the bounty. For me you get out of an RP situation what you put into it. I find all to often that the bigger gangs spend their time trolling the cops trying to RP with their gang mate rather than letting the RP play out. In those cases what do you expect? I think there is room for improvement on both sides...