I don't take issue with the rest but this:
Its still realistically almost immune to all inderect units axis have in the time window it become awaible. Even after formation nerf.
120mm is supposed to be a superior indirect fire piece you pay a premium for. Again I definitely think reinforce should cost more but when you get the 120 the point is to totally decimate static teamweapons play utterly. And really static gameplay in general.
The thing is that--I've found--the only way to really do damage to blobs with the 120 is either luck or having a pair of MGs to suppress. Otherwise you're very vulnerable to infantry actually getting in your face.
So the 120mm is very effective against teamweapons, but meh against blobs unless you get some MGs there to slow them down. And if that happens, you're very vulnerable to panzerwerfers.
So I think it's a good give and take. I am starting to understand why the OP wants to make it less survivable.
It's just that games where I go for the 120mm is not an auto win. Against G43 pfusies the 120mm will get outflanked and decimated if you're not careful. And a stuka softening up any support weapons prior to a push is devastating as well.
And again again, I'm 4 digit teamgames player so take my opinion with a grain of salt.