In the same letter he ask tav to stay near your ex companions cause they could be useful, so he’s clear that this time he wants tav to also play chess on his side, but it’s also clear that he’s asking you to influence them for a future conflict (and tbh, this is just another BG, cause this is exactly what you did….)
I don’t think that it kills the mistery if they make him more affective, hes still a darker grey character just like Minthara, with Astarion you can guide him to the good path
But The Emperor? you can’t fix him, it is on his way or none, you could argue that hes only putting himself in a relationship with tav to get closer and to influence easily, specially now that both need each other to survive and to rule (in a posible future)
