hello !
I think that would be cool if the evil men of mordor was recruitable. it could have two new avant post for the mordor the avant post of Harad and the avant post of the Rhun.
The current spells of Mordor that summon the Evil Men on the ground are exactly meant to represent a not so meaningless aspect both conceptually and lore speaking.
It exactly symbolises that those people were Allies of Mordor but indeed not bound to them as the other 'ordinary' foul beings that Sauron often managed to gather.
Being not recruitable highlights their status as the 'exotic Allies from far away lands' that they actually embody (coming from the edges of the map at the sound of their horn, to support the Dark Lord).
There could also be other things to say about the insightful and deep difference from the Humans' malice to the one of Orcs, but this is not the Lore Corner, and I know that the topic could 'escalate' rapidly
Therefore, I eventually think that, if Evil Men were really to be added as regular units that are normally recruited in any structure, the creation of a new Evil Men faction would thus be the only most logical and conceptual idea.
And, there is an interesting thread regarding this exact suggestion in the Off-Topic section, which I sincerely encourage you to read if you are interested
