Could you ellaborate on this, please?
Other than that, he's looking good. And if he can travel through space, we can get him into the RP earlier.
Shifters are too powerful, sorry. He can have up to four alt-modes, though.
Just a quick comment on this part of his backstory:
The Prime colonies actually haven't had any real wars. Sure, there's been some scuffles with hostile aliens over time, and relations between the colonies have fluctuated over the ages, however the Knights of Cybertron and Bellator's warriors have been able to keep things from getting so bad.
So while Piston might've seen some action in his years, I'm not sure it'd be anything too major or traumatic.