I think that should also be the case in vanilla. Maybe they could be called Thracian Rhomphaia Bearer. I'd even give them white clothing just to push against that internet myth (black is just reinforcing it).
I've never mentioned their effect, but I was thinking, as with cultural things like the Theatre, that they could expand a building territory when garrisoned in it (by a cumulative percentage, they should have a count limit anyway).
I did a little research cross-referencing data on how to do it for an RTS scenario.
The first step, as in any effort to tell a story, is this:
Stage 1— Establish the historical period, belligerents, political situation, strategic circumstances, and events leading to the battle.
What happened before the scenario?
Why does the battle or operation matter?
What are the commanders trying to achieve?
Output: Historical briefing and narrative premise.