For some reason, Hasbro had a really hard time explaining Headmasters to the general public. It seems like a natural evolution of an idea, robot changes into things, robot's head now is the pilot of thing it changed into. This lead to fiction of two minds sharing a body, where in Japan, the head just controlled the body when connected. I like Takara's take on the concept better, simple is usually better.
It does make me wonder why Hasbro chose to make the Headmaster a different character. Part of me wonders if they planned to make the Nebulons a thing. Like, down the road, individually packed Nebulons or something. Takara did. It would make sense if that was the original plan and things changed. Later they revisited the idea in Titans Return and it was a pretty big success. Little robots, drive big robots and bigger robots are also play sets.
I wonder if Micromasters was ultimately the evolution of that idea. I mean, obviously it was in practice. Little robots turn into little things and have play sets that transform. Maybe that was the idea of having the Headmasters be separate characters to begin with. Like, it just occurred to them while playing with the prototypes. Or on the toilet.