Just a wee bit of input - I think we ought to try and avoid modern unit designations like numbers and corps / army group / task force etc. There really wasn't a whole lot of uniformity in unit organisation during the timeframe the Empire mirrors. As a general guide I've found the following to work:
- A company is the smallest unit and on the table could be represented by a detachment. The company does not break down into platoons or squads; such terms were not developed until later. A smaller group of soldiers would simply be called a group or some other unspecific term like "patrol".
- A regiment is the basic building block of the army. This is represented in game by (wait for it!) a regiment. Regiments are commonly named after their commander, their place of origin, or some characteristic feature/location/person/creature/event they associate with.
- It's become fashionable on this site to refer to a Parent regiment and its Detachments as a "battalion". This is not strictly necessary as the whole group could come from the same regiment, with one or two of its companies being the detachments. The term battalion can, in fact, refer to any grouping of units smaller than the army as a whole (as opposed to the modern version, where the batallion is a subdivision of the regiment). Merriam-Webster has the right idea: "a considerable body of troops organized to act together".
- A bunch of regiments form an army. There really isn't any hard and fast organisation above or below that.
- A particularly large army may be divided into divisions - van, centre, and rear. These have more to do with marching order (the van being the most glorious position, and thus reserved for that nobleman who has made the largest contribution of troops or money to the army) than with any tactical consideration.
- Several armies operating together (usually because the land can't support much more than a few thousand hungry sodliers at a time) can be called anything, really - "crusade" if the Church has a strong hand in it, "grand army" if the overall commander is feeling very confident, or even just "army". Specific naming again is usually achieved by adding the overall commander's name, or the principal location the army operates in / draws its troops from, etc.
- Some terms like (grand) company, brigade and corps are used interchangeably for regiment-level units, mostly at the whim of the unit commander and/or owner looking for a more fancy name for his unit. The same applies to a group of regiments belonging to the same commander.
- Knights operates in companies, it's quite rare to have these units - or indeed any cavalry unit in this age - referred to by another name, although the high-tech Pistoliers and Outriders could be referred to as squadrons.
As you can see, it's really a very muddy affair
Therefore I'd stay away from nomenclature that suggests any significant level of uniformity above the regimental level.
