I would like an explanation for why Keira runs off with Lambert at a time when you are desperately looking for sorceresses to you know, save the world.
She does say if she knew what would happen in Kaer Morhen she wouldn't have agreed to come. As far as I'm concerned she and Lambert have done enough. And in the ending where she does find a cure for the Catriona? I'd consider that an accomplishment just as important as helping Geralt defeat the Wild Hunt.
In regards to the endings of certain characters it would be nice to have some more screens during the epilogue narrating what happens to them:
Phillipa Eilhart - Does she actually manage to become the Royal Advisor to Emhyr or Ciri? How does her future look? She does have a tendency to get out alive of some nasty situations and you could say they are indebted to her. Or do they find the voice of reason and decide to decapitate her once and for all?
Dandelion / Priscilla - Some closure to their story regardless of which ending you picked. You might as well say Priscilla never recovered her voice in the Witcher ending since it's never mentioned.
Triss / Yenefer - I want to know their fates regardless of which I chose.
The witchers Letho and Eskel - I never asked them to stay at Kaer Morhen and I'd like to know where they headed after the battle. Would they still meet with Geralt from time to time to catch up? Is any heard from again ever?
The Baron and his family - Does he find a cure for Anna, does Tamara ever forgive him or is at least able to stomach his presence if he sobered up?
Avallac'h - I just assumed he went back to the world of the Aen Elle. He's a mysterious character but that doesn't mean he shouldn't at least be mentioned. He does sustain a powerful spell in the Tower that must have taken it's toll on him. Is he well, disappeared without a trace or ever contacted anyone again? Is there hope for peace with the Aen Elle now?
The remaining members of the Lodge - Does Emhyr fulfill his end of the bargain? I'd assume Empress Ciri would've but Emhyr did betray Letho and I see no reason why he wouldn't do the same to the Lodge. We know he lets Yeneffer go during the Witcher Ending but what about Rita, Ida, Francesca? I assume Fringila will be in the Touissant Expansion.
Zoltan - Think he'll stay with Dandelion as some kind of bodyguard? They make an excellent pair. Still hope to see specifics. He paid off his debt to the King of Beggars in my playthrough so I want to know what he's up to now.
The Crone who survives (Weavess?) - After the fight with Imlireth, Ciri shows up with another wolf medallion. I thought maybe Geralt gave her the one he took from the impersonator in Lindenvale but then again Triss' pendant is still with her even if you let her landlord take it so maybe it's a continuity error? Fix that in this case or show us how they took those back.
There's probably a bunch of characters I forgot, in which case I'll add them to the list later.