The early rules of football were very varied, as can be seen in the different evolutions of the game. Even however once the clear path to seperation between Rugby and Association began to develop there were still a fair few oddities in football. For instance it was allowed to catch the ball and get a free kick from then, no pass backs, etc...
One which seems quite interesting to me is the allowing of handling the ball but not catching or carrying. i.e. the hand of god is allowable.
What if this entered into the rules of the game and remained established there?
Things could really strange quite a lot...Corner kicks would be like games of volleyball, everyone trying to punch the ball into the goal. Punching strength would in general be such an important part of the game.
On the other side of the field keepers would be supplemented a lot by defenders.
I'm uncertain which would win out there, more goals or less.