If spoilers are alright here, then I also was able to do this with the door greeter in the host club (the mouse), although it is a lot more difficult to pull off due to him being right next to Mezz when first entering. On that note, I was able to get to the intended guest and initiate the game with him without wearing the costume, and after beating him, the mouse seemingly goes back to his original position and everything proceeds fine as if this segment was done legitimately. So while it is obviously unintended, it does not seem to be game-breaking for this particular part of the game.