The only vehicles that would have been ok to scale down would have the Vulture Droid(the single release version that was in the boxes that are the same size as a Jedi Starfighter were waaaay to big, IMO), and to a lesser extent, the Hyena Bombers also.
I thought the original released sized Vulture Droids (EpI 3-pack, then in the ROTS Deluxe pack) were fine. Maybe a teeny bit larger than those would be perfect, but I just always felt the Jedi Starfighter sized Vulture Droids were quite a bit too large.
The 1 other vehicle that I have a small gripe with are the large winged TIE Fighters. I mean, compare them to the Falcon now(yes, the BIG Falcon), and the wings look far too large. I never had any gripes with the original ones if put in a diorama hanging chasing the Falcon look perfect.
Having said that, however, nor do I have any gripes with the lager winged TIE Fighters ----however unlike the smaller ones, the larger ones do look out of place next to the Falcon. They look great as a "stand-alone" piece, but not with other vehicles. I think maybe a "Mid-size" winged TIE could be a concept?