McClellan and Meade also They could be but on that hospital/camp set,+ adding some nurses ,photogtapher, war correspondednt ,vivandiers etc.
Under Confederate militia i was thinking those boys that attaced Union troops in film Gods and Generals in Battle of Bull Run also like those militia soldiers like Bill said are usefoul.
Also i was thinking good zouaves for both sides.
And as for the artillery i was thinking normal sige artillery
2 moratars + crew
set 2 Big guns + crew

italery artiller is toylike both the guns and grew but like strelets GNW artillery sets are superior so they should make a good set. ,,Gatlings indeed thidn used in war but this gatling shown in psr site is The model here dates from the early 1880s and is fed by the circular Accles Positive Feed Drum that is on top of the barrel. It is accurately modelled and an interesting-looking weapon, but it has nothing to do with the Civil War´´
So i was thinking that it should be like did they used in civil war. and furthermore i was thinking one set of colored soldiers ( film Glory)

Naval landing parties etc

As for the moundent cavaly als mybe dismonted cavalry Morgan raiders etc

There are mony possiblities