I find that fighting SP with a core force larger than a company become tedious micro-management as I spend a lot of time moving every squad and heavy weapon individually. However, at company level this is fine and fun.
Historically, I know the Germans, in particular, frequently organized groups of units of different branches. I think the term for such units of battalion size was Kampfgruppe. I have memory of reading that there were other Kampf- - - names for such composite groups from brigade to company, but I forgotten the details and would appreciate it if anyone can enlighten me.
One of my favorite SP sets of scenarios was an old SPII set recreating the engagements of the book Team Yankee, scenarios which as far as I know have, sadly, never been updated to SPMBT. The armour heavy company team plus a few attachments was just a very nicely sized and varied unit for long term play - enough different arms present to explore, but not so large as to become a second career.
I'm currently fiddling around creating a 1939 Wehrmacht version of the Team Yankee armour-heavy company team type force and was wondering if there was a historical precedent for such a force at the time. Later in the war, of course, the Germans had all sorts of adhoc composite units, but I'm wondering more about intentional TO&E type company-size mixed units.
I suspect if any group might know about such things, this is the one.