As long as cons and penals aren't scaling and killing more stuff then it kills them, maxims will always be used over them.
Everyone is sick and tired of using shocks and guards doctrine and the only way not to get roflstomped is to spam maxims.
Just nerfing maxims won't fix anything except for making soviets UP at all but early mid game stage.
Same as volks. Just nerfing or removing panzerschreck would not solve anything. It would only leave OKW without any proper AT solution.
I would buff Penals, and nerf maxim... for example remove or decrease maxims point capture ability.
Maxim spam would lose serious capping power without breaking maxims performance... while the soviet player should choose between heavy infantry gameplay with penals or light infantry + support weapons with conscripts.