REN isn't a company level game (I was one of the testers on REN that took to release and fwiw am working on some other MP projects in development) - it (MP and REN in particular) uses the same standard ground and time scale as NB does. Manpower in units is more or less the same as NB- but it sort of depends upon the formation being represented as you sort of have to work with NB unit designations to represent something that was not so clearly delineated.
Example - a Spanish pike block in REN typically exceeds 1000 men in a single unit (not a company

) ... also technically not a regiment - and depending upon how you want to code the pdt and the oob -it also doesn't technically need a single weapon -you can set things up to create a pike and shot capability in a single unit (you just need to play around with some of the math to represent different amounts of guys in a single unit doing different things...).
Anyway... none of that has anything to do with the graphics. Trust me - those are re-useable ... I have done it already when playing around with BPW.