Shinji Mikami’s final Vanquish blog post shows an interesting, but unused concept for the game. Early on, Vanquish didn’t have Sam as a pilot. Instead the suit was a transforming robot three pilots controlled remotely.
Each pilot had their own set of skills such as shooting, melee, and hover/sniping. This made the robot versatile, but players had to switch between pilots and presumably styles of play.
Mikami wanted to focus on the interaction between the three characters like Kamen Rider Den-O. I suppose Mikami’s comparison is akin to how different Imagin give Ryotaro different personalities in the tokusatsu series.