The bayonet thing comes down to how you take that quick deploy bayonet/rifle combination and employ it with other gear. Yes, you might have a split second switch between the two, but that split second switch is there for everything else too Grenade -> Rifle, Mine -> Rifle, Wrench -> Rifle, etc.
The only way I could do it in No Mans Land was to dedicate a special class which had strictly two things: A rifle, and a bayonet. Another, with a Rifle, other misc melee weapon, and hand grenades. And a third, with a rifle, misc hand weapon, and rifle grenades. Making three rifle classes, each with their own specific abilities. The latter two were limited, to 1 per squad.