Alternatively I do think that a good-aligned paladin could still fit into the game. Minthara is likely to be exclusive to the Absolute path, or at least exclusive to destroying the grove, which a lot of players aren't going to want to do. So I think given that, doubling up would be forgivable. A dwarven paladin or monk would be my ideal in that case.
Minthara is paladin class (however shocking it is). I doubt we'll get a second paladin.
But I agree there should be some way to spare her if we decide to wipe out the goblins. This one companion immediately deprives us of two others, and it is not even possible to immediately accept her into the party. In addition, we will lose a bunch of characters (and probably quests and items) that we would otherwise have met in Bladur's Gate. As pleasant as sex with drow women is, she seriously asks a little too much in return. It's not a good deal, it is not convenient for us.
It's actually ironic because the bad guys should get a better deal, but remorse.
