If for some magic reason devs allow br1 have machine guns, wich ones for every nation you would add group for squads
It would be quite complex unless they are MGs like the MG08 and the other Maxim MG variants or something like that; they could also be limited to use only when lying down, like the Japanese Browning .303.
Even the Chauchat is BR2, so I can only imagine stuff like the Puckle Gun or Organ Gun. Or maybe they should just make the Chauchat BR1
They should just drop all the underperforming br 2 mgs down to br 1 like madsen, chauchat and breda mod 30
Anything available pre ww2
The reality is that most belligerents had capable MGs available by 1939, Germans had MG34s and ZB26, the British had the BREN, the Japanese the Type 11,96 and 97. The Soviets had the DP-27 and USA various types of BARs. Even the French had the Chatellerault 24/29. Sometimes is better to leave things the way they are, to “fix” an issue does not make something necessarily better.
USSR: Madsen (not that hard), potentially add some clipper-feed DP-27/28.
Axis: Breda 30
Allies: Vickers-Berthier or add Chauchat
Japan: Type 11 LMG