While there's no specific mod for vanilla Sins that does this, I've done it for SoGE, so I can just put up the files needed if someone feels like doing a version for Sins itself (GalaxyScenarioDef editing is required).

Yes, because it's an addon and not avaliable by default.

I don't follow. What do you mean by "follow the phase line like vanilla"? What I've done is essentially put an invulnerable phase gate at every planet, for each player, one that doesn't reveal any of the map as it's a cargo ship entity. The actual phase gate buff has an absurdly high stack rate, 99 or so, which as a result allows it to stack for every player.

That's the problem, its been done several times but none of those people have stuck around to update them. People who make bigger mods tend to keep them updated because they've invested more into them; someone who just wanted to learn to do this for their own gameplay, then shared it with everyone, tend to not keep up with it.

That said, its not a terribly hard thing to do if you're feeling ambitious and want to put an end to this cycle.