So to try and spice up the mechanic role, maybe add a tuner, that only a mech can use so that he can tune cars directly from a laptop or something as such, so that mechs have the opportunity for people to come down to the shop more, instead of ya just going around the city 24/7. And also instead of the basic car upgrades the mechs have another option for the right price of putting illegal upgrades on cars, that if caught with the car would be impounded ect. Risk/reward kinda scenario. It just improves the mech job and gives us another way of making a bit more money on the side.
long and short.
tuner laptops (mech only)
illegal upgrades (slightly better than the normal, maybe add a few more upgrades (decat, straight pipe(louder exhaust sounds) illegal chips)) and stuff like that!