UEF would burn the gate if they could. Colonists' reaction is irrelevant to this strategic point, since the destruction of the node would mute them on Sol's side.
I think it might be possible that the BP team could try to go this path. First, you need to prolongue the war and create enough war dynamics in order to get an opportunity. Second, you need a plan of attack. In my perspective, it will be a battle of wits between those who defend the node and those who attack it. Diversions, stealth mechanisms, surprises, etc. will be tools for both sides.
Now, if the node is destroyed, I think that the war either escalates atrociously, with general Steele feeling suddenly very alone in Sol and deciding to conquer Earth to prepare it for the next built node; or it will wither, with many tevs defecting to Earth. It can also be a combination of both and lots of insanity from tev admirals, commanders, etc. Either way, it's an incredible achievement for the UEF forces, and therefore they should be working to get this done.
It may however prove to be impossible. With that in mind, we can also see the return of shivans... and then all hell breaks loose.
I place the destruction of the Sol gate and the isolation of Earth for a second time to be the LEAST likely path the BP team would follow, allthough I suppose it's possible. Issue with this whole plan being, it would render AoA completely moot.
The impression I'm getting is that the Vishnans have a showdown planned. Not one of flashing beams and exploding ships, but a psychological test for humanity... and those evil evil Zods. Judging by the dialogue sequence between the Dante and the 'OMGWTFVISHNANSHIP', this involves finding a way to truly create rather then to simply destroy. Cutting Sol off from the galaxy may constitute a 'win' for the UEF, but would in my opinion, almost certainly be a failure of the Vishnan test.
I've never been one to really like the ordained flavor of the Vishnans and Shivans roles in BP. Or rather maybe that's to strong, it's simply not the direction I would have taken personally. However, that doesn't mean I can discount it in context of the story, meaning the only thing the UEF can really do at this point is hope Byrnes (sp?) project helps to provide the 'enlightenment' required. Or its calling for help from Vishnans/Shivans. I can't remember where I first saw that idea pitched, but I thought it was plausible.
Also the Vasudans fit into this somewhere, since apparently Khonsu is so friggen awesome and is already 'closer to enlightenment' then some of the Eldars, which means the node can't be collapsed or else all the storytelling around the Vasudans both in mission and in lore would also be rendered ultimately pointless.
