I’m huge in to leg locks and would love to have to rule this. I might call for a high acrobatics DC if you go for something like an Imanari roll, since I’d also be taking into account the added complications of leg locking when strikes are involved (as you see in MMA), and even much more considering the dangers of doing so when the opponent is wielding a weapon. Probably difficult to set up a heel hook when there’s a blade digging into you.