Nope. It's been done. All you have to do is remold the thighs to collapse down in robot mode to "shrink" the character, and allow the chest to angle in for Trailbreaker's more heroic build.
I don't own the X-Transbots version, but you could easily google them to see how they do the differences. But it can be done with simple remolds. And achieve perfect cartoon accuracy.
