I'm not really sure about the amount of cash I mentioned above, so people don't bust my ...s for it. Because I don't know what the amount is already for the cop job for instance, so just make the paychecks sensible.
Payday payments are based on xp earned. It's based on job rank, too.
For example, a cop's base payment is $64 per 1xp earned. But they also get an extra $1 per rank, so as a rank 10 cop you get $74 per xp.
XP is awarded proportinate to the effort/risk/significance of actions, as you alluded to. For example, an arrest gives you more XP than a ticket.
So yeah, this is already a thing..
You also get an arrest bonus payment currently.