You design actually looks like it would work well for a classics Kup figure, if Hasbro were to ever be so inclined. Not so sure about the head though. Doesn't really feel like Kup all that much, given how G1 the body looks.
OK, with the old body style, there wasn't enough room for the legs, so I'm making the transformation similar to Salvage from the 2007 movie-verse (which I'm surprised to have not seen a kitbash of yet). Alt-mode is the same, here's the new upper body for the robot: