I enjoyed it in past titles of the Halo franchise and miss it dearly.
Spent a while pondering about it and came up with my own version of it.
It works a bit like Skyrim,
Two Handed and One Handed weapons & if implemented right, it could work.
Switching to your back weapon with two One Handed weapons dual wields the Primary and Secondary Weapons.
Zoom & Grenades are prohibited while dual wielding.
Switching again (Putting away the Secondary Weapon) allows Zoom & Grenades.
Primary Weapon
Two Handed
-Assault Rifle
-Battle Rifle
-Covenant Carbine
-DMR
-Light Rifle
-Needle Rifle
-Plasma Repeater
-Storm Rifle
-Suppressor
One Handed
-Boltshot
-Magnum
-Mauler
-Plasma Pistol
-Plasma Rifle
-SMG
-Spiker
Secondary Weapon
One Handed
-Boltshot
-Magnum
-Mauler
-Plasma Pistol
-Plasma Rifle
-SMG
-Spiker
I have no idea what weapons will be returning in the next title so I named all of them.
Perhaps the secondary could just include weaker weapons? (Magnum, Plasma Pistol, Plasma Rifle, SMG)