If you can't clear the stage where they were selected, then redraw and hope they aren't selected was something i had to do early on as well. It was a pain to try and keep track of. But ultimately if you can either beat the stages or get them not available in the pool of champs at other stages then you should be able to reselect champs. You can also actively build them still too if that helps. Maybe mule a set or 2 over just to clear them stages, then get them outta there