Hmmmmmmmmm
Tricky
But possible, take a lot of work and wouldn't look good unless it was smooth. I'm not sure about the stunts, whether or not OFP could cope with something like that.
Shifting your weight option would be cool, but again you might have to wait for OFP2 cause I ain't got a clue how you would do it. Maybe you'd have to redo every animation for the bike so hes sitting in a custom position. (I mean scrapping what they have at the moment and making your own). Then it'd be a long process of doing the anims. (Flips, Wheelies, Stoppies? Stand on your head kinda thing ;D)
If you did then it'd be possible to have lots of fun with tricks on moving veichles. Going off subject how about James Bond style moves. Holding onto the back of a car whilst it drags you along OR standing on the roof and using a weight shift to hold on as you hurtle up a country lane.
Back to the subject the idea of the bike/car going into a plane would be funny. Kinda wacky if you had a chase and then reach the highway, Later guys and press the red button. Away you'd go --- it'd be another great addition.
I think the problems are OFP or skill. It'd have to be a damn good group of animators scripters. Lots of hard work.
(sos for such a long reply, I got carried away with this one beacause I think stunts and moving veichles go together nicely)
-supershooter