I can think of a few vehicles that could stand to be done as well as re-done.
-Naboo N-1 starfighter - w/ vac metal parts, and working droid socket (which would require an R2 unit with telescoping dome)
-Trade Federation Battle Droid transport - I think this has a much greater likelihood of being made than the MTT. The MTT is just huge, and this seems like a more attainable goal with some genuine play value. As for getting my own MTT fix, I think that I might have to make do with tracking down the Pepsi MTT cooler.
-Gungan Bongo - This plays a relevant enough role in TPM that it could do well with the kiddie audience
-Dooku's Solar Sailor
-Republic Gunship - Carrier
-Republic Assault Gunboat
-Yoda's Kashyyyk escape pod
-Bail Organa's speeder
-Clone Turbo Tank
-Theta class shuttle
-Imperial Landing Craft
-Rebel Hangar pilot transport
-Snowspeeder - resized - The snowspeeder is really a small vehicle, and you can see the most striking contrast between the cockpit of the vintage toy (your figures swim in there) and the cramped cockpit of the vehicle in TESB.
-Twin pod cloud car
-Jabba's Sail Barge
-AT-ST - new sculpt - the scenes with Chewbacca and the Ewoks in the AT-ST really showed that the vehicle should be a twin seater. Given the current state of the AT-AP, a more accurate AT-ST should be an attainable goal.
-Ebon Hawk - Why not go for one of the coolest EU ships of all time?