Personally, if I were designing a stronghold, either it would be defensible everywhere, or there'd be one "weak" point that is actually a giant and extremely nasty trap. So, it can be effectively defended against all directions. It doesn't make sense for there to be one giant hole in the defenses, unless the attackers made it themselves. And it isn't necessary to force players to follow the same path to take a base every time. That just makes people bored of the game sooner.