One, development of a magazine-fed semi-automatic weapon to fire 40x53mm HV ammunition from a recoilling over-the shoulder barrel. Such a weapon might have an unloaded weight with bipod up to the 12kg of the M240 MG and yet be acceptable at platoon level provided it could deliver radio and impact fuzed 240gm projectiles accurately to say at least 300m, and 900m against area targets.
I haven't seen this sort of solution in the works, but it sounds interesting. Over the shoulder has worked well for one of the most prolific weapons, the RPG-7 for ages.