as for new Autobots:
Prowl, Smokescreen, or Bluestreak(all the same design but one of them will do)
Dinobot or bots, as long as there is a Dinosaur transformer i'm good, ohh and I highly think they/him should either be like G1 dinobots, or like BW Dinobot
and they should have at least one flyer, possibly Jetfire....Powerglide POWERGLIDE!! and thats it for new Autobots
as for the Decepticons: Megatron will most likely be back, haha just now I was thinking about having the Cons' spending the whole movie trying to resurrect Megs but thats pretty close to what happened in TF1, except SS was the leader and they were looking for the Cube and perhaps unknowingly didn't see that Megatron was right underneath or on top of the Cube but pretty much in the same location..as for Gestalts....as I said with the Dinobots you can't have all 5 of them in the movie together fighting at some point, but with lets say the Constructicons, you have limited action of them as 5 cons, but most of the action involving them is them fighting as Devastator( the real Devastator)
SS will obv. be in it
but that still leaves more spots open for more Cons'
Soundwave
other Seekers who will want to challenge SS's authority and try to resurrect Megs
Astrotrain or Blitwing, just cause they're triple-changers
if NO constructicons, then Tidal Wave or Trypticon
the point of this is this......G1 had a ton of bots, some were more prominent than others, some had specific characters for each episode, BW had far less bots on each side and still had time to concentrate on 2 or 4 bots per episode with not a single appearance from others
YOU CAN INCLUDE ALL THE AUTOBOTS AND DECEPTICONS IN TF2, BUT MINIMIZE ON-SCREEN APPEARANCES FROM OLD CHARACTERS