The idea is that you can charge your shield, and gain an extra layer of protection. Like the sword of Nero (if I'm not wrong) in DMC4: a meter that injects power from the mist (not your mist enrgy from your tank XD), once the meter is full, you get another layer of protection.
If this is taken into consideration, a maximum of two / three layers per player (with a one-time / monthly upgrade for an additional shield layer, maximum is 5 layers) so that the game is only affected by a slight margin.
Or, for diversity, a special offensive force field can also be added (instead of another block layer) for a set amount of time (for some shields).
Or, like, an explosion if your guard is broken...
My two cents. XD
UP!!!!