This would be awesome, but I can’t imagine it happening due to the ripple effects of some players controlling a separate character in the narrative. Old content wouldn’t make sense and new content would have to create multiple instances of dialogue any time a relationship or past event is mentioned with the player. I don’t think it’s impossible, but it does limit what they can do and adds more work to the pile.
But if they did do it, I would love it if veteran players got a prompt to recreate their character (as if using a fantasia) and then when they went to meet with the scions, Derplander would be their old WoL.