I think a Shadow the Hedgehog esque morality system would be good for a Waluigi game, just with a much more comical tone. A lot of fans have already taken to Waluigi as an anti-heroic or plain villainous figure and would be disappointed by either being set in stone as canon - not sure how you'd go around a morality system for a fast paced linear platformer like I'd expect this to be though. Would be really fun in a collectathon though.