Q: How much detail has gone into depicting the specific factions, is there specific music, and language on the battlefield?

A: Yes, we've localised the playable factions. French troops speak to each other in French, regardless of whatever language you're playing the game in. And you get orders shouted out in that language. Music and battlefield music will also be thematically linked to where you are and who you're playing
YESSSSSS!

That's one of the biggest things I missed from Shogun and the original MTW. The people shouting orders in Japanese, Latin, Arabic and Russian...good times, good times. Themed music too? Great!