UPDATE: I'm currently working on a new version of my mod, which will (hopefully) fix the unit recruitment issues and any bugs/inaccuracies the current mod has. Currently, I only have Russia and Britain fixed for the full non-beta release. Here's a preview:
Great Britain
A combination of three nations (England, Wales, Scotland), England has a good deal of diversity, ranging from Welsh Fusiliers to British Infantrymen to Highlanders. The British regular infantry are the best shots in the game. Their melee abilities are average, so they can hold their own, but they aren't as proficient in melee as they are in ranged combat. Highlanders, armed with bardiches, provide an elite melee backbone to the armies.
Pros: Excellent infantry, strong cavalry
Cons: Small unit numbers
Tsarist Russia
Russia is a vast country, the largest in the world, and it also has nearly unlimited manpower. Regular Russian infantry are atrocious shots, but are superior in melee to the other factions. Also, their units are very inexpensive, giving them a good number advantage. Though most are poor shots, Hillmen from as far away as Siberia and beyond provide the firing backbone, and are overall the most accurate irregular troop in the game. The Russians fight with fierce determination, and can prove quite an opponent despite their shortcomings.
Pros: Excellent melee troops, Hillmen are excellent shots, Can use sheer number to win the day
Cons: Regular ranged units have dreadful accuracy, Inexperienced units