How would you tell Seven's last BF story?

I have very mixed feelings about this. Think about the Doctor’s final lines in the series: “There are worlds out there where the sky is burning, where the sea is asleep and the rivers dream; people made of smoke and cities made of song. Somewhere there's danger, somewhere there's injustice, and somewhere else the tea is getting cold. Come on, Ace, we've got work to do.”

I like the thought of Ace and her professor voyaging forever onward, as young and vital as when they spoke those words. They never get tired, they never get old, they simply go up and down and to and fro across all the worlds bringing hope to those who need it most. If we never have an ending, we can believe that they’re still having those adventures even after Sophie and Sylvester are no longer recording them.

This is a situation where we don’t merely tell the story because can; it has to be that we tell the story because we must. The story will have to be so good that it will be a crime not to tell it.

Problem is that we had several conclusions already. A Death in the Family could have been a perfect end to the Seventh Doctor’s run. I think it could have even served as a conclusion to the main range. Likewise, there is a story about how the Seventh Doctor comes to terms with the Elder Gods that have been giving him so much trouble, and that was another suitable ending, or something close enough to it that it doesn’t matter.

What I don’t want:

The Eighth Doctor. This should be Seven’s story. I don’t care for the Eighth Doctor as a character, and the last thing I want is the implication that he’s fixing his predecessor’s mistakes, particularly in Seven’s final story.

A retread of the Six Doctor’s Final Adventure. That was a great story. It was suitable epic, it fixed the problems with canon without ignoring them and it gives Colin the good death he deserved. But the Seventh Doctor is different character in a different situation and a carbon copy retread would do no one any favors.

What I want:

Box set: The format worked very well for the Sixth Doctor and I think it would work here.

Different companions from different eras of the Doctor’s career. Mel’s not my favorite, but she was the first, so Mel, Ace, Hex, Rayne and Klein would all have to be there. Heck, since this is my fantasy, we’re bringing back Ray from Delta and Sally and Aristedes too.

The baddie is a Bad Future Ace, which is revealed in Disc 3 as several seemingly unrelated plot threads pull together. She’s learned all the wrong lessons from the Seventh Doctor. Remember when Davros tells the Tenth Doctor that he turns his friends into weapons? He realizes that’s what he’s done to Ace.

There’s a brief line in the second Klein trilogy that never got much attention, but the Doctor mentions that he’s set the TARDIS up as an ad hoc monitoring station because he’s concerned his next incarnation won’t be willing or able to protect the cosmos to the extent that he can.

Near the end of the story, The Doctor knows he will have to become the Eighth Doctor in order to prevent Evil Ace from coming to pass, and he struggles if it’s the right choice. Not only will he die, but so will countless others down the line because he will become someone who can't protect them. He makes the decision to stop Ace when she kills Hex and Sally and their children.

The conclusion to the set comes as the Doctor steps out of the TARDIS into the hail of gunfire that he knows will kill him. The ending is bittersweet and its canonicity questionable as we reveal that the Doctor has prevented Ace from being swept up in the time storm that started it all and she is living an unremarkable life in Perivale.