You can't make the hog model any bigger than it already is in game w/o mods. So really you can only make it smaller than the original. About your question... I have no idea.
But you can take the wheels off, make it drive several feet from the ground, and somehow give it a cool wind effect under it.. that would look sweet. A hoverhog.. I have been looking for one of those to download.....
Hmmm, you'd have to remodel, fix the animations, re-work the collision, and then test it out using trial and error until it's perfect. Very time consuming.