I guess I can understand why they didn't go the Titanmaster route, because the original Doubledealer was a Powermaster, and those little guys turned into engines that were more rectangular than head-shaped...
So it looks like the Transformers guys at Hasbro thought about that with Doubledealer, by releasing two cassette-bots as Knok (Rumble with new head) and Skar (Ratbat with new head) as part of a 4-pack in the Generations Selects line (which means two separate purchases to complete Doubledealer), AND... they gave the Doubledealer toy a place to store one cassette (maybe both?) to homage the original toy having one Powermaster plugged in to unlock one of its two alt-modes.
As for the cat scratches on Megatron - the Netflix trailer actually has Megatron with deep gashes on his chest, so those paint apps end up being cartoon accurate, even if it looks a little insignificant on the toy.