Random masks sounds strange.
Not really. Let's say that Mian have around 8 different masks. I think those masks have an order to appear: mask01, mask02, mask03, etc. And at certain moves she changes her mask. So independently which move she does masks change in that order in loop. So we can see one same move with different masks depending in what you do during the match. Let's say the first thing you do with Mian is her Climax. Then you'll see her Climax with mask02. But if before Climax you do a move where she changes her mask and then the Climax, you'll see her Climax with mask03.
If i'm right, then Mian is probably that character impossible to do in 2D Oda refered to. Because do all that mask changing for all possible frames would be insane.