dAGGER: I think a minimum number of moves with no capture is a good rule to force a draw, if one of the opponents claims for it:
1) it is simple to remember for everyone
2) it helps preventing games to go on years, when only a player is very slow
3) if two skilled and defensive players agree on going on, it does not oblige to end up the game as a draw, if no opponent asks for it."

I agree with dAGGER completely. For this reason I think the rules shoudln't be too different between the various variants, best would be 1 and the same rule (x amount of noncapture moves maybe with an addition of beginning after move y)