Motonobu isn't one of the "four generals" guys then? I didn't know that, I thought (by process of elimination) he was probably the fourth one. They never introduced any of these characters, really... so the fourth one is some guy they haven't mentioned yet, apart from that he's not there. As for the villains, I didn't remember their names, but yes, given the completely different costumes and the different color scheme, it is easy to tell them apart at least.
Also, yeah, I thought the idea was for those four to be the core of the plan, so as I said I was confused when one of them apparently knew nothing about it. I guess Motonobu didn't think he'd go along with it, or didn't think he was trustworthy, or something.
Oh, and on the note of Motonobu, at least this plot does give an explanation for why he expelled all of his retainers in favor of robots... he was planning this action all along.