I've done some thinking about this, and there are two ways to go about it...
1) You put the
props into a standard GT game.. that means your Batmobiles will do about thirty MPH (except the Tumbler, that mother's fast), your General Lee is an automatic, etc. They'd be novelty cars, really.
or
2) You make a separate game.. maybe a $20 title or something.. "GT Hollywood". The cars would then be "real".. Your Batmobiles would all be 150mph+ monsters, etc.
The problem is that there aren't that many cars out there, really.. Probably just a few dozen truly unique vehicles from various movies that aren't just "normal" cars.
But, here's a few that I thought of, in addition to the ones you already listed:
KITT
THX-1138 police car (which wouldn't be much of a stretch.. the base car is already in GT4)
Eleanor (Gone in 60 Seconds)
And probably a few others that I can't think of.