That scenario where Triss or Yennefer are waiting for you to talk to them once you're done with pretty much "everything" to trigger the Ending credits would've been a great idea.
We get something similar to it in the ending where Ciri becomes an Empress, sadly after talking to Ciri and finishing epilogue we can't get back to that point.
I'd say the epilogue White Orchard with Triss or Yennefer, Dandelion, Zoltan are waiting there (Since we're done with the zone) for Geralt to get back and decide to finish it is a great idea.