It's far easier to have squad differences built into a unique weapon than to have individual squad modifiers on everyone. It's easier to see the balance when all information is in one place. Squad modifiers are a huge pain in the ass and lead to other imbalances, such as captured weapons being far too strong on a squad that picks it up.
I have personally designed a few of the weapons of Soviets. The stat changes are very simple, take only a couple minutes and do not delay OH in the least. The OH delay is not related to Soviet balance at all actually.
Trying to change it like you want it is actually far more complicated, less efficient and more difficult to balance. We can make much more precise changes that don't affect other balance when everyone has a specific, unique weapon for them.
Finally, it's not really your problem to worry about weapon stats so don't worry yourself over it. It works very well in the current system and that's all that's needed. An overhaul would be far more time consuming and confusing. If you have a balance concern, bring it up. However, leave the actual mechanics behind balance to us, and the devs who help us.