Personally I've not played many 4X titles, but what I would want is stacking troops to form squads. This would be 2-4 troops of some kind along with a NCO. This would just occupy one hex and move as one unit. This can then be turned into a platoon with 2-4 of squads and a CO. They cannot all stack into one hex, and each squad must be in their own hex, but the entire platoon can move at one, or you can move each squad as their own with lesser movement range.
At any time, a squad can break off from a platoon and at any time, a squad can break off into multiple units again. I honestly don't think it would be smart to move into larger hierarchies (companies, regiments, brigade, etc...) as you would get to a point where you have a blob of hundreds of units moving at once unless you stack even more troops together. And of course the names would change for various types of units. Navies could be Squadrons and Task Groups, Air Force can be Sections and Flights, etc...