1. if you can't be bothered to do something right, why bother doing it at all?
2. Why do people still think brake fluid is a good way to strip paint from plastic?
3. If you want to build a street BMW, why not start with a street BMW kit? Dragon, Hasegawa, Tamiya, and Revell have all made them for the E36, and they're not that hard to come by. The painted Dragon ETCC kits are rare enough and cool enough looking that I would leave it as is, and get another kit to build with it.
The short answer is, the Dragon prepainted kits are rare enough that few if any people have tried to paint over them. It's laquer, so logically, if you use anything but laquer over it, it shouldn't react. But I wouldn't try it.