Well, even 50 people armed with clubs, bows, and the occasional rifle are going to get mowed down by a walled base armed with defensive turrets, surrounded by punji stakes.
In addition, if the worlds are big enough, an intelligent player or group of them could simply set out on an hour-long expedition to somewhere well out of the way of roaming bands of goons, and set up a concealed base.
In Minecraft, (with mods, of course) for example, it's entirely possible to build a fully functional base that's literally invisible to the outside world save for a single, easily defended, entrance. If you're going for a block-based sort of thing, then a combination of player-crafted, very tough blocks, booby traps, and hidden turrets and so forth would make a base nearly impossible to find, a massive pain in the ass to break into, and all but guarantee severe casualties for any roving band of looters.
If such a base could be found and its defenses neutralized, it would be earned through teamwork and blood. That is proper PVP, and I would play it.
There's also the problem of defining "griefing". For example, in EVE Online, for many players, about half of what they do on a daily basis would qualify as "griefing" in other games. If it actually was, then the entirety of New Eden would be a lawless hive of scum and villainy. This is not the case, and non-consensual PVP is not necessarily griefing. For this game, I think an EVE-style system like that, supported by your automatons (CONCORD) would be ideal. It might also be an idea to take some inspiration from Wurm Online and their phantom guards or whatever the hell they're called. Basically, in Wurm, players can build huge guard towers requiring hundreds of bricks and tons of mortar, all of which must be mined, chiseled, and mixed by hand. They can then gain the services of a few high-level ghostly guards granted by the Gods or whatever to defend their lands... For a fee, of course.
Now, in your game, maybe there's some super-rare crystal that would allow a player to build additional, lower-level automatons after purchasing a permit from the Empire at some exorbitant cost, or something.
or there could be a requirement to display your real life name from the credit card you signed up for your account with and keeps a profile of your history on the game (lack of anonymity and accountability makes everybody 10x nicer. It works for some online newspaper comment sections pretty well and people are willing to sign up still)
Are you trying to engineer failure? Because that's how you engineer failure. You're also opening up the possibility for someone to get fucked over in-game in a rules-friendly way, and then, in their anger, falsely accuse the conspirator(s) of some kind of real-world crime. Inevitably, this would turn into a massive media shitstorm, probably ruining the life of an innocent guy who was just playing a video game.
You also may be forgetting that most people play video games to escape reality, not be forced to be tied to it. I would not play a game that people could use to track me down in real life. Why would I, when plenty of games out there already don't?