The only problem with m9k is that you can shoot through props.
Bit we can easily put rules in place.
After that m9k is miles better in every regard.
What Chris said
As for the vehicles, would you rather give players the ability to toolgun vehicles?
I thought it could be easy as this is already available if you hold C then right click a car there is "body groups" so if you was to add this into a NPC it would add great RP (My opinion)