I was thinking the Shield-Nades are not too good,So I came up with the idea of actual shields,They will have a smaller HP than Shield-nades but you can keep them forever,and when unequipped it is in the back,protecting you from the bullets that come in your back,And there will be 2 Shields:
Plastic Shield(Not so good,Cannot protect you from explosives,Breaks at around 500 Damage)
Metal Shield(Solid shield,Can protect you from 2 Grenades,One direct hit with the Grenade Launcher or Rocket Launcher,Breaks at 1500 Damage)
You cannot shoot while holding the Shield