A new TM Megatron would be cool. And I suppose a new TM Cheetor would be nice, but honestly, the original toy was pretty cool, and it's gonna be hard to improve on that.
TM Megs is also on my shortlist of TM wants, since his original toy suffers a rare offshoot of GPS; but also means we need a TM Primal as you know people are gonna want both leaders.