Keep in mind any changes to the Stug to improve its viability will inadvertently reduce the viability of the T34, which also seems to be a key concern within the community.
This issue is fairly complex unfortunately.
I can totally understand that, it can't be easy balancing a game like this. That being said the stug rarely ever gets built since waiting 25 fuel for a p4 makes so much more sense. If the T34's viability will suffer from giving the stug a cone viz ability, then give the t34 a slight buff to make it more viable?
Thing is just that its kindof irritating that the russians can field an su85 so quickly (roughly the same time as germans can field a p4) and have extremely long line of sight. I dont want to be forced to go the elefant doctrine to get scopes to be able to see the su85. Vision is everything in coh, and his su85 can see my movements and basically 'spots' for itself.
Here is an alternative solution: (just theory-crafting...)
Bring back the "spotting unit element" we had in vcoh. I used to love to get a bike to spot for my stug mid game.
Thus give the german 221/222 very long sight range, or a spotter ability when standing still, so you can at least see the su85 when it can see you.
Give the m3 the same spotting ability as the 221/222.