+1 to all of this. As well some other ideas that could be added:
Phone charger - A lot of people who have/have not been in DCC have suggested that every spawned taxi+ should come with a charger.
Updated phone application - We have some vehicles that still need to be added to our phone application ( Patriot2, Enus Cognoscenti and XLS ).
Scripted taxi request permissions - Let's say a trainee accidentally accepted a stretch request which is only allowed for senior drivers+. The script would prevent certain taxi requests being accepted by people who don't have permissions for that vehicle/call.
"Debt system" - Currently you can abuse each taxi ride if you do not have any money in your bank. What could be done is an implemented script that would take out money either from the persons salary, or from their bank whenever they redeem their salary.
Currently that's all what I'm able to think of. If more ideas come through, it will be added to @ImSteveHi post.