While I would love to see Aneska in the game I feel it would be VERY odd to use her on Hades Betrayal maps. We already know we wouldn't be able to use her on Destroyer of Worlds, this makes sense since you can't use other former bosses on their own level. But the other characters who were former enemies or people you save all make sense. Loaht, Kuzman, Shae, Schneider, Lycus. Ayana, etc... you fight or save these characters at the BEGINNING of the campaign so as to make sense why you can use them on the rest of the campaign they're from. Schnieder falls for Mikah and joins, Kuzman is captured and is forced to joins, Loaht is save and so joins, etc... and the Campaigns have no cronology relative to each other, they're isolated adventures, Council apocalypse being the only one that has a clear chronology (protectors die).
But when it comes to Aneska, sure you could use her on all other campaigns, because it could easily be said that she did those missions AFTER she joined Harec. But, it would be silly to use her on ALL the Hades Division maps, because she doesn't get defeated until the very end. It would seem silly if she was fighting with you on Low Blow, In Medias Res and Double Agent only to ALL OF A SUDDEN turn against you on Destroyer of Worlds. At least Kuzman explains on Upside Down that the one on your team is a clones, so this is why you can use Kuzman. I feel she should not be a playable character on the entire Hades Betrayal campaign, because it doesn't make sense.