The point of run blocking is to create momentary holes for a RB to run through. This also, means that the defense can run through the same holes, but because the ball carrier has gone downfield, it no longer matters how many defensive players are in the pocket.
Your idea will work, if all you really want to do is give the QB a couple of extra seconds, because it's pretty easy to run around a run block, it just takes extra time. In theory, a pass block can be sustained a lot longer if the Olineman is good enough.