Making the sov sniper one model will not fix any of the issue's plagueing it (impossible to kill with infantry or 222).
It will only make it possible to countersnipe it with ostheer (terrible design and sucks to be okw eh?)
Snipers need a straight up nerf, they shouldn;t be a hardcounter to infantry as they are now.
Make Ostheer, UKF and Soviet snipers only killing models that are under 90% life. So they become support unit and not anymore offensive ones. Thus the need to kill them decrease, you can counter them with healing your squads. At the same time, spamming them become less than a viable option.
As using the sniper, two different functions are defined:
Scouting but with the impossibility to kill anything that is full life.
Effective support behind a squad of gren, a HMG etc... picking wounded model.
Snipers could have a cost decrease to compensate.
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In my opinion, I would redesign completely how snipers are working.
First I would decrease by a lot the threshold to kill vanilla models. Something like putting the threshold at 65% life and apply specific modifier with veterancy.
Example:
Vet0 Sniper vs Vet0 Infantry = threshold at 65% life
Vet0 Sniper vs Vet1 infandty = threshold at 70% life
Vet0 Sniper vs Vet2 infantry = threshold at 75% life
Vet0 Sniper vs Vet3 infantry = threshold at 80% life
Then the sniper veterancy would provide some modifier on those numbers to reach, maybe, 100% at vet3 vs vet3 infantry.
The achievement here is that snipers are less powerful on the early game where they completely dominate because of lack of effective support (of any type) and gain power not by killing and killing low vet infantry but when your opponent gain his own veterancy. The objective is that having a vet3 sniper vs vet0 infantry would do nothing effective.
So calling a sniper early game would become a long term investment, and anybody playing vs it would not need to panic early game to find a way to kill it right of the bat (and most of the time fail miserably because early counters are not that effective in fact), but building a strategy to eliminate him before your own infantry veterancy plays against you.