And there are few more ideas that i'd like to bring for your judgement.
As an alternative way to end the Museum storyline, player could mix infinity stone, Green meteorite and 5 nightmare cubes in the Cup of Hebe. Why would you do that? To create a Tesseract Cube. An artifact that is equally as dangerous as impossible.
It acts roughly like the infamous Ghost Machine. Except for one thing: instead of giving units to player it... kills you. Well, only in 1% chance. So only the exceptionally misfortunate (posessed) or hardcore players will hesitate using it.
Usually it will just grant you one of random items from items pool. Usually.
But beware! After using the cube 10 times, every time you force a prisoner into the Tesseract cube, you will have a 12,5% chance to be dragged into a nightmare-ish realm. And this is where the fun begins. Because the poor souls are being transformed into something else. Imagine a vaguely human-shaped insane mass of flesh, hornes, eyes, screaming mouths and other nice things. Well, you'll encounter plenty of those. More specifically - number of prisoners you pushed there divided by 100. So yes, after some time using this cube becomes a risky thing.
After reaching certain rank in necromancy monk character could find new recruits by preaching on the streets of towns. Depending on charisma, player can be either ignored, attacked by guards or succesfully recruiting farmers to his/her party.
Farmers should be upgradable to acolytes. Aside from that, it could be a good idea to make acolytes upgradable using their experience, if necromantic upgrades are unavailible for the player. Of course, such options should be limited to "evil" equivalent of sea raiders or mercenary swordsmen at best. Speaking of necromancers, it'll probably be a neat idea to make them generate troops of their type. I.e. bloodpreservers generate preserved zombies, shadowlords generate brollachan, etc.
It may be slightly overpowered, so it might be a good thing to limit the spawn, depending on player's party capacity. So when party is 50% or less full, they will generate with the 100% frequency (same one as Hawkers') 52% capacity - 95% speed, 54% - 90%, etc.
Making 2-3 alternate bodies and enabling random heads/legs/hands would be just fine for them. Otherwise they look like their master deliberately chopped their heads off and sewed exactly same bits together to make his troops identical.