Not sure if you're implying that EPS in general is a problem, or just in the Mirage's case.

Because the 2015 Canadian spec Nissan Micra has EPS, the same tight turning radius as the Mirage, and it steers quite "normally". Pleasantly, actually. So, EPS can be done right.

EDIT: also, I'd imagine you should just be able to take the motor drive out of the EPA unit and essentially make it "manual" steering, which would dis/prove the "EPS is the culprit" theory. I guess that's what you're investigating?

I don't think it is the culprit.