So this works, in that it plays the epilogue after the final dialogue of the game.
However there seems to be a dialogue bug:
with avernus choice still seems to be ignored in the epilogue.
(IE if the love interest goes to avernus with karlach, the epilogue seems to ignore it. and the cutscene that used to play of them both entering the hells no longer plays. )
it seems like the love interest just ... stays in faerun after agreeing to go to the hells. (jaheira's dialogue seems to be the only one that seems to recognize the choice)
