TakTom designers do MPs from scratch to finish (Hasui's drawings are awesome...) they certainly have the capability to design awesome robots without Hasbro's creative input.

I've been having this theory that the reason Hasbro not doing any actual industrial design/engineering is that it might just be too expensive to hire someone to do in-house in the States. They do have someone to check-up and test-out the final design (from the Gizmodo interview a while ago) but I really doubt if they can make it without TakTom's engineering capabilities (the Titanium series was completely done in-house IIRC and it wasn't the finest work in the franchise)