For defense against outside threats:
A wrought iron or chain link perimeter fence would serve as a barrier without providing cover or concealment.
I've seen a couple threads about people legally shooting intruders through the door as the intruder was attempting to kick it down. So sturdy exterior doors that aren't bulletproof might be a good idea.
On a similar note, you might harden the wall on the strike side of the door full height so you can have good cover while at the door, but leave the wall on the hinge side unhardened, or hardened only up to the windowsill as others mentioned. Then design the porch such people have to access the door from the hinge side and won't be able to take advantage of the cover on the strike side.
In the front room you could build a hardened pony wall around the basement stair opening located and oriented such that you can cover the front door, windows, and possibly even the back door while standing on the stairs. In the basement of course you will have your safe/storage room with all concrete walls, floor, and ceiling, maybe this is under the porch. And of course in that room will be the secret door to your escape tunnel, because as long as we're throwing around ideas, you might as well have the tunnel.