My original intent was to wargame the Italian Wars. But after reading Irregular Wars I fell down a rabbit hole and came across the 1529 Siege of Vienna with Landsknechts facing off against Suleiman the Magnificent's Ottomans.
Irregular Wars seems to fit what I'm looking for – mid-sized battles played with a modest number figures on a small table. But in case I wanted to use another set of rules in the future, I decide on a flexible set of basing – stands 50mm by 25mm. I'd use four of these stands for a Pikeman's Lament unit.
Four stands together on a movement try will give me a unit for Pike & Shotte or Basic Impetus 2.
And two stands on a tray will form a unit for Irregular Wars.
One final picture of the compulsory units for an Imperialist force for Irregular Wars – two units of mercenary pike and two units of mercenary shot.