That sounds very interesting, but I think it would be simpler to create something similar to the Commando Triangulation device, making them limited to 2 or 3, and making them only possible to spot by snipers and enginers. It might be a bit more fragile but it would work in the same way, without being to OP (hiding troops inside, being too hard to find since not everyone uses buildings, etc.)
I would also give it an extra ability to bring in the Sniper Ace instead making him come out of the buildings like Partisans
OR (a possible reward unit to exchange the sniper ace with) Partisan Commanders which are close-range but large LoS spotter units that can be attached to the Partisan squads similar to the British officers and confer the bonuses of higher LoS/ spotting range and to capture territory faster.
Perhaps when Vet is introduced he can also act like a Captain for the Partisans (since most partisans were civilians/ soldiers that escaped from the German encirclements or got left behind, they didn't get any new ranks, while most partisan COs were in direct contact with either the Soviet Gov't or KGB) providing them offensive bonuses., but i don't want to get too carried away here
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