To make a henchwomen for another race would be straight forward to do from what I've done.
The core files that I changed are because of some memory issues (I get headless people), otherwise I wouldn't have to change any files.
So you need to change the coreracetype.xml to add in your created characters as well as set up the generic_henchwoman.
you need to add <GenericUnitType_Other>Generic_Henchwoman</GenericUnitType_Other> to coreracetype. Limitation seems to be only 1 of these hence the reason why they're only henchmen and not women. (If I could get this to work I would have added it to be able to make both). As it is you could add this to the file and then you can have altar to ONLY make henchwoman. Fits with Relias womanizing in my opinion.
Next you need to add to each of the coreabilities.xml, coreclothes.xml, coreitems.xml, to force the modelunittype to use the clothing items and abilities to design your own units traits and items.