Now, I know that this is a disliked topic due to the lag it would create, however I am still wondering why there would be so much lag. In my mind i see a method as follows. The grenade launcher attachment could be used as an additional button, like the Lexel Rifle. However, this button would not act like the Neo Rifle where different modes must be selected and used individually. Instead, you tap the grenade button and there goes the grenade. Then it automatically goes back to gun operation.

I don't think there would be lag at all and this is why. The glauncher could be handled like tossing grenades the old fashioned way, except with a pffloom sound over it. The grenades will have the same function as before except you aren't vulnerable to gunfire when switching back to your other item slot. In addition to the reload pause to match the thrown version, there could be an automatic reload just like guns reload.

When selecting which grenade type you want to use, you just go to the grenade inside your inventory and equip it to launcher. So this could free up an item slot if you usually use grenades as your secondary. That slot could in turn be used for a melee or anything else useful in combat.