I think this new shot of Alt Grimmy looks even less bulky than before, especially those thin thighs. He doesn't look that beefy at all. Also, what the hell was Takara thinking leaving the entire floorpan as kibble on the back hanging off his behind?!? Could have swung up or come off and been a shield, but NOOOOO! This isn't Grimlock, this is someone else and that's how I'll accept him (plus, Grimlock would never have bucket seats for feet! ).
I am pretty sure the movie is nowhere near far enough along in preproduction to have influenced this Alternator's design (or vice-versa).
As for the scale of the beasts and whatnot, I think having big insects would make the Decepticons even cooler - the humans now have to be saved not only from jets and tanks attacking them but big robotic insects smashing their cars! They wouldn't be part of the earliest waves though because how would they be "robots in disguise"? Same with the dinosaurs.