What your suggesting would be a tremendous break with tradition and I don’t see that ever happening. It would be essentially the half and half H and M wanted....well, really just for Meghan, which wouldn’t have helped Harry, who apparently has wanted out for an long time. Before continuing in this vein, I want to add that it’s disappointing for me that Harry chose not to continue as a working Royal, knowing that someday his father would need him.
Anyway, I don’t see why the BRF would have to soften their stance. From H’s perspective, he married the person he was supposed to be with, so it’s just as well that his previous girlfriends broke up with him. I don’t think because Harry was unhappy that the BRF has to adjust their policies, though you’re right that Charles could do that in his own reign as he has his siblings. Still, I don’t think of that as workable overall because, depending on when William becomes King, he may need all the help he can get until his kids are old enough. Then, if that policy about only spouses of future monarchs being working Royals were in place, even if all three kids are old enough, I don’t see there being nearly enough people to support William.