By switching from only thinking of man-to-man and fantasy table combat in Chainmail arena, I've opened up conceptually to a hopefully cool idea. I'd read that Gygax thought fantasy rules should only be paired with man-to-man, but several examples of the game in play, as well as many notes in the fantasy supplement, suggest using fantasy creatures in mass combat.
The mass combat rules will probably speed up games. Since I plan to play these play-by-post, that will help. Faster is always better in PbP.
Also, with each mook-type unit representing a troop of 20 (or so) combatants, it allows each to be flavored as such. I immediately thought of Magic: The Gathering, where usually cards for weak monsters represent squads. Like the classic Mon's Goblin Raiders or the Orcs of the Iron Claw. Yes, there are some individual weaker monsters, but I like the idea of players not recruiting 20 generic "light foot" or whatever. They have to recruit Atalanta's Amazon Skirmishers.
And I plan to fully take advantage of pop culture/fantasy media/D&D iconic characters for heroes, antiheroes, superheroes, superantiheroes, and wizards of all stripes. Conan, Elric, Simon Belmont, Warduke, Strahd, Merlin, Circe, Melisandre, Madmartigan, and so on. Makes sense to also have some flavor for the squads of troops.