Well, I've held lots of tourneys (80% of the people here use keyboard) and never had this problem at all. But I see people are still concerned, I guess it's understandable since competition is serious business. Banning keyboard is really drastic, though, since MBAACC is a PC game and you play those on keyboard. So here's the solution:
People who'll want to use keyboard should bring:
- 1 usb keyboard without any key
- 10 keys to put in up, down, left, right, A, B, C, D, Q & start
There are people who use the left hand for diretionals and people who use the right hand, so 4 configs are needed:
No customization allowed. Distance between diretionals and buttons should be the same for both hands and both sides.
Alternatively you can just remove the keys your opponent is going to use from your keyboard. Just don't forget to remove windows, esc, alt, tab, etc, f's, etc.