Hooray! Finally, a defence is possible!
I suppose this does mean that it's possible for a player to seal himself off from the rest of the quadrant impregnably, by closing all warp points out of his grav-shielded systems and abandoning any colonies outside of that group to remove the possibility of intel. But since grav shield facilities cost a fortune and take forever to build, it's likely that this will only account for a small number of systems. If he ever decides to reopen the gates to the outside world again, he's likely to find that he's been left behind by the massive non-isolationist empires out there.
