MrMormon: I don't know if this would be a variant per se, but it would be an interesting experiment to have two (pro) players/teams do the following:

1) play out a full game (alternatively, allow step 2 at any time)

2) the loser (either if a tied or uncertain score) picks one of his/her/its previous moves and plays differently

3) play the variation

4) repeat steps 2 and 3

If one or both players got bored, others could take their place (same with team members). I don't know how long a game of Go Back would last, but this could be a great learning experience. If only we could find the correct komis this way...

Should I put this under variants? Is there already a page on SL about this? If not, should I start a game? It could become a very large page.