Lynxara
Nice post!!
I disagree here. I don't think it would have worked without Enter's previous interactions with Hiromu. the new guy would never have thought to used Hiromu as a back up if he hadn't been defeated by him previously.
Yeah, but Enter doing that had nothing to do with Enter's character, or their specific interactions. Another character who knew of Hiromu's actions in the past could easily conceive of the same thing, especially if he was the type implied to have been watching the whole show from off-camera. It is a really obvious thing to do once you've realized that Red is indispensable (in either setting or genre terms).
And frankly, there was no actual reason for it to be Hiromu, save that he is Red and ergo Sentai's nominal main character. Logistically, the plot works out about the same way if it had been Blue or Yellow. They'd do most of the same things Hiromu would've done in that situation. Using Red just means your villain can make an evil Red suit, with has more visual appeal and plays with the audience's expectations.