The Gnome Editor is in the MTW Files section, or the Downloads section, both off of The Org main page. With that, or with Excel, you can change anything you want. You can change the build cost and the upkeep cost. If you like smaller size units, you can reduce the unit sizes in that file too. So like you can shrink spear units to 50 men, archers and swords to 30, and cav to 20 or whatever.

If you're trying to tweak the game such that the unit deploys fewer units, but still normal size units, well I'm not really sure if you can do that without screwing other things up. I mean, increasing the two cost variables might do that, or the AI might decide it has to spend less on buildings so it can spend what it costs to build build armies...who knows.

Personally, I like smaller battles, and maybe even smaller units, though the smaller unit sizes also affect routing formulas and such I think, as those might use whole numbers and not % of unit size, I'm not sure about that.