Wouldn't it be much easier sometimes to being able to simply swap your primary weapon with your secondary by pressing a specific button (I believe '4' is for example currently unoccupied)? Especially if you are on a zombie hunt with a melee weapon, it would be kind of cool if you could simply switch to your shotgun if you risk getting overwhelmed? And I know that by pressing 1/2/3 you can get either a firearm, blade or blunt weapon, but what I suggest is that the weapon you had equipped just before pressing that button simply moves to the secondary slot instead of going back to your inventory