i think every faction needs a different roster. even if you just edit names/stats a little, it goes a long way. i'd rather have Russian Cossack Line Infantry -with boosted accuracy, attack, and hiding skills and lowered reloading and defense skills- than run-of-the-mill russian line infantry with roughly the same stats as just about every other euro line infantry.

every country needs different units, stats, and appearances. no one faction controlled the whole of any continent during the 18th century; the balance is already there. all we need to do is copy the 18th century units and stats, and we have an already balanced game!