Oh quite, as a plot element its got a lot more going for it. And if shoehorning needbe, Primacon could have always helped Unicron into the final stages of the form we know, from a mechanoid planet similar to Cybertron of the G1 cartoon to the full-on Unicron planet/bot. Primacon's initial systems could have guided it until the spirit within the shell awoke and broke free. I just can't buy the Quintisson origin. Almost anything BUT that. Shrewd businessmen and opprotunists don't take millions of years to rein in rouge appliances. Can you picture a 500 year old vampire trying to rein in an antique toaster oven? Or would he just got buy a new toaster oven?