Indeed, but those characters don't necessarily have to be controlled by players and, usually, it's best if they're not from a GM perspective. Otherwise you get shit like, I dunno, a submissive shotacon Napoleon or some other Nasuverse-style complete character mishandling, to the point where it's the character in name only. And then there's the issues in giving established and important characters to something as unpredictable as a player.

Anyway, for the mecha, you might want to look a bit into Escaflowne. The show itself is a fairly boring slog through a teenage girl's love triangle with two pretty men more often than not, but the very underused mecha are pretty damn great. They're these weighty titans, capable of swift or precise motions but overall heavy-feeling ground stompers controlled by strapping the pilot to a clockwork contraption inside a cramped cockpit with little vision from which they have to coordinate the machine's motions, which they control by straining their own bodies to boot. [url=https://www.youtube.com/watch?v=vwaOO-xNYnc]This here[/url] is a pretty good look at how the machines function and their overall style sans any manner of spoilers, I think it should fit what you're looking for.

No offense but your proposed idea for the powers and mechs makes the two things kind of unwieldy and oddly incompatible, since you need to stop and very openly expose yourself to use your abilities in spite of rather than because of your mech, not to mention it'd be something that has no relation to the Navirez, which I gather are something of a central aspect of this whole thing. Not to pat myself in the back or anything like that but I feel custom-made Navirezes designed so the Revolutionary can use or even amplify his powers via (insert fantastical mechanism related to the nature of Joan's curse here) would be a nice way to further link pilots to their units and make them more than just regular warmachines.