Aye...'tis already created, but may be held up a bit, as it's not going to be a standalone kitbash. There's a fair amount of other material that will be coming out along with it.

There are plenty of papercraft car models on the net you can get for free. I got a wide range of car models from Volks beetle to Chevy Camaro, to Jeep Cherokee. You have to adjust the size of the print out a bit to fit in with Mayhem scale but that is simple to do.

These posts are a couple years old. A number of sets now include cars, and there are numerous vehicle kitbahes.

Yup. MPD, Mayhem Bank, Mayhem Industrial, Shellendrak Manor (and it's expansion) and now Mayhem Junkyard all have cars and trucks of various sorts plus there are several vehicle kitbashes available.

Wildwood has Limos also