i won't to obligate to you use quake engine but in case u don't know there was a lot of conversion for car racing, aircraft fighting, soccer, etc...
plus there are different open source engine based one with bump mapping, colored light and other improvements

i didn't check the status of these projects recently but i think they are consistence.

don't forget the huge amount of editors u can find for textures, skins, maps, quakec etc...

the problem is the license

btw hope u'll find what are u looking for and remember to keep us update