I thought it would be cool if there was a way to mix up where you find joinable npcs. It is hard to not meta game when you know where everyone is e.g. heading north from the FAI to get Ajantis or east to get Viconia, when you have no reason to go there until much later.
Certain npcs could be randomly allocated to the early game, mid game and late game so you still have access to new npcs at different stages. Tiax could be either preaching in Beregost, hanging out in the Cloakwood or at his usual spot. Ajantis could be in his usual spot, chasing bandits in Cloakwood or at the Temple of Helm in Baldur’s Gate. Xan could be held hostage by Iron Throne members later in the game. Branwen could potentially be a statue in a couple of different places.
It would force me to work with the people I met and approach playthroughs in a less contrived way.
I guess some npcs could be more difficult, like the canon team, especially Imoen. Though Jaheira and Khalid could have left the FAI but you can catch up to them later, even in Cloakwood or later.
It may be a lot of work but could be a fun mod?