Stage diversity isn't a factor in this scenario.
When a player loses a match, we are giving them stage selection advantage going into the next stage. Just because they lose a match on the stage they selected doesn't mean they should not get the same level of advantage they had during the prior counterpick.
Wins and losses themselves are not penalties and should not be penalties. To remove a stage from a player's list of CPs because he lost on it penalizes that player further than receiving a match loss and rewards the opponent further than receiving a match win for having defeated them there.
It seems like your message is to promote stage diversity over set fairness.
When a player loses a match, we are giving them stage selection advantage going into the next stage. Just because they lose a match on the stage they selected doesn't mean they should not get the same level of advantage they had during the prior counterpick.
Wins and losses themselves are not penalties and should not be penalties. To remove a stage from a player's list of CPs because he lost on it penalizes that player further than receiving a match loss and rewards the opponent further than receiving a match win for having defeated them there.
It seems like your message is to promote stage diversity over set fairness.