I have a points cost system which determines unit sizes:
I'm using huge unit sizes for those who prefer larger battles, like me. For anyone who prefers smaller they can change the in game settings down to large, normal or small. Much easier than the other way around as most mods do; smaller in EDU and force everyone who want larger to code it in themselves.
As with everything in the entire system, I switch and change parts to find the right balance, and that would include points value vs unit size. Currently warriors of chaos are at 190 troops and chosen foot at 150, which may be too high for balance sake, but I've yet to play a campaign. Too many small units can be easily overwhelmed in med2, so there's a fine line between sticking to lore/tabletop and gameplay. It won't be rushed out though, if it feels or plays wrong or is too hard changes can be made.
I also have a system to determine unit build times and refresh times based on the units points costs, whether they are core, special or rare and I've also included exceptions for some factions and troops. Orcs & goblins having a minus 1 refresh and build time, all undead have a build time of 1, dwarves, high elves and dark elves add 1 refresh time across the board, plus their better units have even further recruitment penalties. Wooden artillery also has a minus build time, while experimental empire artillery increases.
It's a full system covering everything, which will need testing and refining once I have a playable campaign.
What I'm trying to achieve is a balanced but very challenging battle on the battle map, with a balanced auto resolve for the AI vs AI, while also limiting special and rare units in a way other than giving them far smaller units.