I believe giving points for capturing stones is a bit problematic. For instance, imagine that there is a simple ko shape between two players who are behind on points. They could keep trying to take this ko back and forth at the end of the game, both gaining points. This is not a fool-proof plan to get them in the lead, they have to avoid repetition, and other players can interfere in various ways. But it still seems like a weird thing to give out points for moves which capture back and forth without progressing the game.
So the option I didn’t think about but which maybe works better is rather than players gaining points for helping to capture stones, instead the player whose stone is captured loses points per stone captured.
I just read that this kind of rule was being used at the go variants server when posting here Go-variants as templates - #12 by shinuito .
It just reminded about the discussion here.
