You can make huge fundamental changes like "you cannot connect 3 stones in a row" or you cannot make a certain shape with your stones. There are 'bad' shapes in

You can make huge fundamental changes like "you cannot connect 3 stones in a row" or you cannot make a certain shape with your stones. There are 'bad' shapes in go that you learn when you're young that almost never surface in higher levels of play (of course you would make a non-bad shape illegal). You can say every 15 turns you get 2 moves in a row and they are stagged (this is game-breaking). You can ban certain josekis ('standard moves' early in the game). You can make each captured stone worth 2 points instead of 1.