Tacticle Sling

Hey guys,
If got an idea, how about a "Tacticle Sling" for most of the primary weapons?
So you can switch your primary weapon faster to explosives or other things.
Please let me know how you think about it and maybe it will add to the game.

I assume your character already has a sling - otherwise I don't know what happens with the primary when switching to sidearm or a grenade.