Actually, I'd throw in behind highly trained non-sentients being able to pilot SF:1 mecha, or drones or something. Happens from time to time in anime/Sci-fi universes, so there's OOC precedence.
Not too sure how it'd play out, though. Less needed cockpit space could mean, um... well, you'd be able to armor the thing more, put it in odd places, and so forth. Maybe certain species (uplift series -> dolphins) could be sustained in a liquid environment, which could mean higher achievable gs and faster mecha. If nothing else, less needed space could mean more guns. That's always good.
Really, just some way to take dominated critters into SF:1+ combat would be neat. After all, robotics has the potential to make piloting allies, so why not let its alternative have the chance too?