Thanks for your input guys, I'm now leaning towards the platoon scale campaign. Could call it
Platoon Leader!
At this scale there's a number of ways I can make it work, using the action cards.
They would be centered around abstract support from the parent battalion.
The deck of cards would be refreshed each campaign turn.
Examples:
A platoon that wants to specifically attack (or a platoon that is weak and expects to be attacked) can get reinforcements in the form of an extra squad for that turn.
There might be something like 3 of these to be distributed by the CO each turn.
Similarly, battalion reinforcement cards might be a machine gun section or a light mortar section, or a flamethrower team or a sniper...or any other support we decide to be in the deck.
The losses of these support units may or may not be tracked (abstracted battalion pool).
Each turn might see replacements trickle in. One green squad can be added to a platoon (permanently) by the CO every turn.
A light vehicle might be available to a platoon each turn.
Probably many more interesting ideas to be considered for the action cards.
Maybe even some special ones issued by the GM to cause trouble.