So, there is a spoiler about the real identity of the Emperor
This is the legendary hero Balduran, the founder of Baldur's Gate
but... that doesn't work? He is explicitly a recent hero, the noble he worked with was still alive for most of the game? he is from BG, does he say this? In the not-romancing him storyline everything you learn about him doesnt make sense if that is who he is? For his secret base and backstory given to work he has be an adventurer from between BG2 and BG3, not centuries earlier?
Minthara is the best character and she NEEDS to be recruitable if you side with the grove! Also- I support the important thread in the suggestions: Let everyone in the Party Speak