Wouldn't she have to be a henchwoman?

With the way they implement henchmens (and special units in general), it's not really possible unless they give altar two special units that essentially does the exact same thing. Not that it's impossible to do, but it does take a lot of work adding in a unit and getting all the clothes and item availability right (hence why all the bugs with horses/cloaks/range weapons/etc).

Not in a quick and simple way at least. The problem is that the henchmen units are using a HenchmenMale model (which is a male model, obviously) so that they can attached the special henchmen traits to it (like they attach golem/jugg traits to golem/jugg models). In order to get a female Henchwoman in the game, you basically have to duplicate the henchmens, along with adding another female model and all, then go through all the items and traits that they should use (and it's different due to male/female clothes) and add in the new female model for those. If you just pop in a female model on henchmen units, they won't have the special henchmen traits attached (and if you attach the traits to the basic model, then all units can use them). It's doable, but that doesn't mean it's not a lot of work... and when they can't even get all the stuff for male henchmens working correctly, well...

Also, it needs to be fixed so that Henchmen can be from any race.  Unless the intention is that only the default Altar race can use Henchmen, which would be kind of sad.  It shows up Henchmen in the Heroes tech item (in the Magic tech tree) for a custom race with the Heroic trait, just that they don't appear as selectable options to train and there is no extra Henchmen option for unit design like there is for default Altar.  Please fix when you can.   At least make it selectable for a custom race with Altar blood, like the Great Axes Juggernaught trait also applies to custom races with Trog blood (AFAIK).

I wrote Reply #7 before the reply in the other thread, so I would say I agree with you.  "These special units seek out every heroic race with sufficient influence" could be used as a good way to explain why the Henchmen look like Altarians, as they are a special group of Men who reach out to heroic races with influence.