if you're 'diving by' a target you're doing the same # of damage (if not less, depending on accuracy) whether or not you were walking, driving, or on a roof- only difference is you're just getting away quicker.
if it was done with bad intent - now there are two separate people (driver/gunner)- (im under no impression that people will be driving and shooting at the same time) that receive punishment punishment- which doesnt sound real meaningful but both of whom presumably have been on the server long enough to get money, buy an smg+ (usually including getting factioned/firearms ids) , id say most people who've been on that long are generally no more of a risk to be a minge than our server base
the only restrictions id suggest are (maybe) restricting assault rifles+ and also preventing people from being able to shoot out of delivery vans, work trucks, and city taxis
e: imo another important restriction; you'd need to prevent people from putting away vehicles that have been involved in pks/hits for at least 10 minutes