There’s literally nobody relevant and known by the general playerbase save for Lilian who isn’t suitable for a host of other reasons (in particular, the will of her own character).
Aelthalyste was a close second in my mind, except Blizz decided to retcon Cult of Forgotten Shadow to having died rather than being the primary Forsaken religion.
The rest are dudes, and for a variety of reasons Blizzard simply isn’t going to replace a Girl Leader with a Boy Leader.
That’s why I really firmly think Calia is the best choice and you can create a Council around her of the various factions/focuses of all of Forsaken society.
Keep Aelthalyste for Cult of Forgotten Shadow/raised by Arthas angle, keep Velonara for Dark Ranger High Elf origin angle, keep Lilian for Lordaeronian Human self-loathing angle, add Delaryn for the Sylvanas-raised Night Elf angle.
So you have a Blank Slate character that can be used to uplift the different parts of the Forsaken, which is arguably better than the Sylvanas-centric Boring Human + Cool Dark Ranger norm we had.
Keep the boys around for secondary council (Belmont, the Apothecary dude, etc).