But the problem is that once they lose the initial element of surprise they are pretty much worthless as frontline units. A simple munitions upgrade that can only be done in friendly territory and boosts health/armour would help them stay relevant.
Partisan have 80 health as other entities.
Since the have cloak and elite an grenade they are not be used a "front-line" unit but as an ambush/recon/support unit especially since they also have access to mines.
Finally keep in mind that Partisans are one of the few unit that does not pay a premium for being able to spawn from ambient buildings, any buff they might receive would have to come with an increase in their price.