Why not give the player a bonus for finding/unlocking a new Bad End? For example after that party "loses" the first game, the next party the player makes will start off at a higher level/with better equipment/further advanced on the map...which of course would open up new avenues for bad ends. As a bonus (on top of a bonus!) you could set up previous heroines as the new baddies for the next stage of the map! Perhaps there are one or two character who make it through most of the map...only to be taken at the very end of the game.
Another benefit of a system like this is that you'd have a perfect reason for episodes of the game to be released over time rather than as one cohesive whole package.
