I suggested something similar. Bolster should have to be upgraded at HQ as it is now but then each squad needs to pay 45-60 muni for the extra man and it would lock out a weapon slot. So you cant go double LMG 5 man and overall need a lot more muni invested into your infantry. That would slow down 5 man Section spam and mean overall less muni to spam on other abilities, mines or grenades.
This is just the best suggestion so far.