Yeah I think the only way to do it currently is Spend Spell Slot, Spend Points, Regain Points, Use ability. If you want to encourage using the ability before you are down to 10 points there needs to be a benefit. If you really want to do it give an extra meteor /5 spell points. Or an extra 1d6/point spent so a level 20 could in theory rain down 30d6 if they blew all their points. Really not that big of a difference considering you can only be affected by one burst and 20d6 will clear most minions anyways.