I think this topic has been turned into a wish list.
There is a major flaw with the proposition of native weapon upgrade.
Giving Cons PPSH will make PPSH doctrines irrelevant.
Giving them DK-28 will basically turn them into Guards.
The only possible adjustment that can be made is through veterancy system but that's only if Relic is willing to do so and that's highly unlikely to happened when you consider their statements as it seems they are happy with Cons as they are right now.
No
The same weapon on different squads already perform differently, IE: Rifleman m1919s are slightly worse than Paratrooper's m1919s
Also, giving them a Dp-28 does by no stretch "turn them into guards". They have significantly weaker rifle dps, would only have 1 dp, and don't have those good grenades.