One flaw I can see, if we're willing to go widely off course.

Zoro's feats, particularly his loyalty feats means he "can't" fight Luffy at his best. Luffy would know that, so it'd be a token effort at best.

So in other words "the evil plan would have gone off without a hitch were it not for the power of friendship and bonds of loyalty between comrades".

The group could always make an exception for that rule cause they figure it'd be cool/they figure out a way it'd make sense.

Zoro's loyalty is nullified if his captain does something unacceptable. Then again, tolerating mutiny is worse to him that inciting reverse-mutiny, so who knows.

I dunno, if he was ordered to have a full on duel, Zoro would probably go all out

Is the plan to just ask 'do you wanna fight?'

I have to assume the plan is for Luke to winkingly go along with the misunderstanding that actually happens in the original.