I would love to be able to "bench" a character for a season

For whatever reason (not really important to this discussion), I've got some champed 5 stars, but they don't really have much synergy. When I go to do PVP I always get my butt handed to me because I have a high MMR. It would be awesome to "put them on the bench". So they are locked and can't be used then they are not part of the calculation of the MMR. Then I can play some fun 4 star teams.