I would hope if we started selling power from EVs back to the grid, that owners would be able to set a reserve amount of charge, and only sell excess above that

I would hope if we started selling power from EVs back to the grid, that owners would be able to set a reserve amount of charge, and only sell excess above that level. And presumably it would only make sense for owners who could charge when demand is less, and opportunistically sell back a portion if demand is unusual high.