So I’ve been messing around with “Hell Bent” and “The Doctor Falls”, and in both instances I wound up using the ending of ‘The Husbands on River Song’ on them. They work quite well.

For the Hell Bent version, you really just edit out Clara and Ashidlr’s conversation and also take out the soundtrack for when Twelve enters the TARDIS, then cut away from him standing in the ship’s interior to a shot of River emerging from the TARDIS into the restaurant near the singing towers, (indicating a passage of time without some cheesy ‘sometime later’ caption) and trim a few things here and there (remove River interacting with Nardole and the other guy in the robot suit), from there it works fair well.

The “Husbands” ending for Doctor Falls made for a better ending, largely because it’s an ending on top of another altered ending. As we know, The Doctor Falls ends on The Doctor resisting regeneration and meeting his first incarnation. In my cut, I infer that Bill’s girlfriend Heather ‘heals’ The Doctor and puts them both back on Earth where they spend the evening talking about Missy and eating chips (borrowing a flashback from “World Enough and Time”), after they discuss the Time Lords, we cut to River coming out of the TARDIS and steps into the restaurant near the singing towers.

This would probably require potential minor re-edits of earlier series ten episodes, possibly ‘Extremis’ to remove any reference of ‘Domestic Bliss On Delrinium’ from Missy. The forwards and backwards narrative of River’s timeline on her end could make it easier to gloss over other things such as Nardole being despatched by River on her final orders to look after The Doctor, which could still occur at any point after The Doctor’s visit in the ‘present’.