I think a Dlc, expansion, or whatever the CDPR does to continue history would be more interesting if somehow it is with some new technology or maybe Nanocells to cure V, and in this process V was finally able to find a cure but on the way ends up killing someone powerful, or maybe a son, brother or someone close to someone powerful. And then you could have a little different story than a complete expansion doing the same thing that the game has as "finding a cure".
This person will want revenge and will want to not only kill V but all the people V loves, Misty, Viktor, romance.
And the story would go on like this, V trying to protect the people he loves and himself from this "villain".
Maybe V would accidentally kill someone or the villain would think it's V's fault, maybe that could happen on this mission at Crystal Palace.
Perhaps the "Villain" is from a Corp that is not yet present in Night City, or the world is quite large and there must be other powerful Corp like Arasaka.
And at the end of the story of this Expansion, it could have different endings too, maybe depending on the decisions your romance would die in a very sad way, or other characters like Viktor and Misty.
V:
-No Panam! Don't leave me!
Panam
-I ... love you ... V.
V: NOOOOOOOOOOOOOO !!!
lol
Come on! Killing your Romance at the end of the game would be another way to make players cry.