Here's some answers to Momotaro questions:
Basic mechaincs- Each stand equals about 500 human-sized fighters or 250 cavalry-sized riders. Groups of 3 to 6 stands are grouped under Battle Group Leader stands. And groups of 2 to 4 of these Battle Groups are organized under a Wing Leader. At the beginning of each turn each HQ rolls a d6 for its activation number, and then the GM draws from a deck numbered 1 to 6 in black and red, with a reshuffle card in it. When a leaders card is drawn, the units directly under him can activate (move or shoot). Morale pips are accrued as units take hits, and these pips must be rolled for before a Battle Group can activate.
All Units are assigned unique attributes (movement, defensive factors, melee attack, reach, morale level, etc) and these can be varied to give units unique qualities. Fantasy units can also be asigned certain special qualities like "resistance to magic", or "less affected by edged weapons", etc.
So, given some of your examples; the attibutes I would assign to the ratman would invlove perhaps faster than average movment rates, less armor defense, a shorter reach, and the ability to see better under night conditions. The zombie would be slow, and a heavy defense, and perhaps a weak melee and perhaps resistant to magic.
Yes, the rules contain a half dozen sample armies: Elves, Dwarves, Orcs, 15th Centurt English, Roman, and Carthiginian
We strongly believed that magic should not dominate the battlefield. Wizards can't just point at a unit and "zot" it into oblivion. Wizard stands represent a powerful wizard and a small entourage of apprentices and lesser wizards. Wizards are assigned a number of spells, determined by the wizard's level, at the start of the game, and once these spells are used they are removed from play. The spells for the most part involve morale effects, movemnt effects, and combat enhancements or reductions. Wizards also have a small shooting ability, similar to missle armed troops, that represent smaller level close-in magic for personal defense, as oposed to the larger "battle magic".
Yes, casualties are by unit. Each combat stand can take three hits before being removed. Leaders, heroes, and wizards take two hits. Hits lower the ability of the unit to inflict damage.
No the game is not tied to any particualr scale. Yes, we use mainly 10mm armies; but as long as the relative base sizes remain constant, you can put any number of any sized figure on them without changing how the game is played. One of the authors, Dave Wood, uses the rules with his 25mm figures:

I hope these answers help. If you have any follow up questions, please feel free to ask.
Here are some battle reports that might interest you:
http://onemoregamingproject.blogspot.com/2014/05/bear-yourselves-valiantly-demo-games-at.htmlhttp://onemoregamingproject.blogspot.com/2014/01/bear-yourselves-valiantly-fantasy.htmlhttp://onemoregamingproject.blogspot.com/2013/07/saturday-look-sarge-no-charts-games-at.html