Unique Classes/Skills/Characters

Something I believe would be more engaging and fun in regards to character recruitment, is having unique/hidden character/classes or at least skills for some of them.

The recruitment mechanic is clearly a major part of the gameplay loop and progression. Personally, I believe having some classes/skills or characters that are unique, and more challenging to unlock(Potentially based off choices) would entice players to go through another playthrough. Especially if NewGame+ is something that may be considered as well. Kind of like having characters tiered, with "Legendary" characters, or at least having them learn "Legendary" skills or classes through quests/choices/minigames etc.
This may open up a lot of squad customization for players, looking to base whole squads around special classes/skills.
If this is something that isn't possible for the game currently, I hope it's something you consider for future expansions/installments.