You could implement an intiutive cover system. Check whether a wall is in front of the player. If there is a wall and he's moving towards it, switch to cover mode. Pressing the backwards key will let him move out of cover. It is the same like with other cover systems, just changes the triggering event from key-press to just moving against a wall.

EDIT: just checked the net for intense third person shooters...
Look at this, Crysis in third person view, doesn't look
less intense.
http://www.youtube.com/watch?v=aSu7GqL5ovo