I think the new model coming out I am most unsure of is the super-crazy-epic-cav-battle engine warcaster... eLylyth3^2 or whatever. I liked that warmachine had the "king" like in Chess. Kill the warlock/caster and gameover, so he or she needed to be well-protected in addition to being well-utilized. I feel like a bunch of crazy battle engine based casters might ruin that dynamic... though, I do trust PP to do their best to balance such a thing in their ruleset. It just kinda screams "much like the colossals, bigger is better... and we kinda ran out of ideas..."
I bet (hope?) my fears are unjustified... and I have no doubt the model will be fantastic!