It doesn’t hurt to allow higher than 9 rank differences, it just doesn’t help either. People looking for a ranked game I feel tend to want a game that’s going to affect their rank, a 1d winning against a 15k though for instance is going to have a negligible effect, so it’s not worth playing a serious ranked game, better to play an unranked teaching game.
For now yes, we are going to be implementing some stuff to better handle that scenario though.