Pre-war Kar98k and Kar98k with both GLs - add ‘can zoom when bolting’ feature (like Lee-Enfield or Winchester 1895). Same for MAS36. And Japan short Type 99s (basic infantry and sniper versions).
MP35/I - 920 maxed RPM with nerfed accuracy and normal 6.8 damage.
MP43/1 - moved to SMG class (it was accepted for mass-production as MP40 replacement), with historical 540 RPM.
MG 81 - lowered movement & dispersion penalties closer to BARs - it currenlty has worst penalties of all MGs despite having a weight of only 9kg and being a BR5 gun.
Neither the G43 or the ZH-29 should be moved down. Give the G41 a modest reload buff, nerf the reload a little on the Johnson rifle, and nerf the SVT-38 by making it clip fed (though buff its damage to its peers at the same time).
I see that you have at least humbled yourself on this point. A surprise to be sure, but a welcome one.
I would be all too happy to endorse this - as soon as someone proves that this was ergonomically feasible with these weapons…
You should not use a administrative trick to fool Hitler as an excuse to reclassify a weapon in-game - this is paper fiction, the MP43 has no quialitative reasons for why it should be recognized as an SMG.