Why not make it so that the Partisans can be reorganized into a regular infantry unit when they retreat to the base? When the partisans met with the regular troops, they were usually poured into the regular rifle units. My idea is that the partisans get the Conscripts skin, change the veterancy ability, maybe even a 5-man squad, but for example with two DP-27 or MG-42/34.
I wouldn't change the skin, but you could slap merge into them perhaps... That may be interesting....
Side note, what about some field reinforcement JUST for partisans? Something akin to pathfinder beacon that only reinforces airborne for the spartisans? Could give them cheaper reinforcement if the beacon is in enemy territory to reinforce that they are resisting enemy occupation and their role therein
That would allow them to stay behind enemy lines a bugger shit up.
Also in campaign they could create blinds that let em set up ambushes... That would be a huge bonus to them as well...