A minor signatory that houses the Joint Operations HQ on their capital base sends a bit of a mixed message, not to mention incredibly stupid. The first place any invading enemy targets is the HQ's, kill the leaders and the forces soon scatter, not something you'd want on a resort world full of civilians. What the old OS&C had in mind when they signed is beyond me but this version would prefer to actually trade with Gallia and preserve it's neutrality as any tourism company would.
If the CR wants to fight Gallia it can by all means, but it will do so without OSC|.
If Gallia ever gets to Cortez.
As for OSC|, you can try nullifying the treaty single-handedly, but you're surrounded by three nations who won't take too kindly to that. Neutrality has been understood, which is why OS&C isn't at all obliged to assist Liberty, Bretonia, or Crayter in combat against Gallia. But trying to throw the whole treaty away because you're afraid you'll get shot along with the rest of them if Gallia reaches Cortez ... won't go over too well.
Cortez is an important system after all, and none of those three nations want Gallia to develop even the slightest foothold. You might think that your neutrality will magically prevent the GRN from using Curacao as a forward operating base (again, if they reach and take Cortez), but trust me, the GRN won't think twice about squishing you. Not to mention that all that any of the three allied nations needs to do, to ensure the treaty is kept, is to park a handful of cruisers in orbit. National defense and all.
Yeah I get it, it was an "untouchable" independent world. Was. Yet for five years inRP (since 817 AS, renewed in 821) there has been this treaty, and if you look closely at the trade lanes, they are owned, maintained, and defended by the two houses. Call it storyline progression, and the fact that stagnation is bad. And while none of the allies are interested in owning Curacao, again because they respect neutrality, they sure are settled on never wanting King Charles to reach it. Because he will take it if he gets the chance.
If you're looking for something far less controversial for Orbital, try investing in what the Vagrant Raiders / Natio Octavarium left behind; Planet Witchita, Kansas. Nice real estate, probably good for tourism, and well out of the way of the war. Working on securing it inRP might be a fun project, too.
PS: No, Highland, CR doesn't. We're focused up north, and even if we tried to grab it, Liberty could take two seconds to beat us over the head.