I'm not a fan of giving it the ability to act as a pwerfer, they need to be distinct and if that Katy can do then it's blatantly better instead of different. There are times when the werfer is better than the Katy, but not if the Katy can alpha strike like the old precision strike.
As I said I think a wider scatter attack with Supression for a cost would offer the Soviet some half not awful blob control. Maybe even half the damage of the rockets.
There is no reason that any unit should have useless vet from Soviet vet 1 abilities to okw vet 4 and 5s. It should all be attainable and an actual improvement.
I also dislike the idea of a pwerfer like alpha strike.
Overall, the idea of incendiarty rounds seems to be the most coherent as it could be apllied to a number of situations. It can be used defensively to cutoff the blob from assaulting a position and could be used to force the enemy to move their support weapons.
But even then, its sounds too much like an flat out upgrade from the normal barrage (don't know how its balanced for mortar halftracks)
A supression barrage will have to do less damage (dont know how to explain it lore wise) but it will outright stop enemy assaults and I kinda dig the "I can supress like a pwerfer, but i have to pay" thing
Stun is another variant if supression is a bit too much