My picks:
-Interplanetary Black Hole Generator; if we are talking about guard posts we are supposed to hate, there is nothing I hate more than black hole machines.
-Flux Projector; Did I suggest this to be a brutal pick? I guess I did. Anyway, my rule is "If you don't like your own idea enough to vote for it, it was a terrible idea", so here we go. Also, @Hearteater. Balanced properly, this would almost be MORE brutal without ships inside being able to shoot out, for two reasons: One, give the post TRULY nasty short range guns, since you know any ship getting shot at by it has volunteered to do so. Two, as soon as something breaches the barrier... everything inside is going to be fully reloaded.
EDIT: Another twist to make it "brutal" without sacrificing the theme of it being "it's own little world": Limit what kinds of ships can cross the barrier. For a nasty reversal, make it so that only ships that are NOT immune to instakill can enter, so you have to use fleet ships (and high-cap ones at that) to take it down. Bonus points if it has an ion weapon.
-Displacement Field Generator; This is a terrible, terrible, wonderful idea. If you combine this with the projection ship from the bonus ship suggestions, you could almost make this whole "mirror decoy" thing a core technology for the new expansion.