Given the Maxim's arc of fire, I don't think you could credibly argue that an unsupported Maxim would be very strong if suppressed Grenadiers couldn't use rifle grenades: a Maxim is extremely vulnerable even to such a "potent" combination as 2 Pioneer squads with *minimum* micro.
The MG42 has a massive advantage as a "leave and forget" type of MG anyway.
MG-42 has a pretty slow traverse speed when it tries to rotate to the other side of its arc after the nerfs it's received.
For rifle grenades, I would say reduce the range or increase scatter, etc when suppressed, but I would also say they need a cost increase to around 30-35 munitions so they're less thrown around in every single engagements, sort of like the old Molotov(still possible, but scripts get eaten alive now).