I agree definitely could be more than one fight filmed there, especially if Greenwich is a doorway and not simply a one time invasion due to a spaceship crashing either. If you recall our lengthy discussion about the column, and how it couldn't have been knocked out by the crashed ship, due to the direction the pillar pieces landed. I think we decided that likely Malekith or Thor were thrown through the pillar from the inside of the building, and then they fight just outside of there where Thor is thrown towards the pillar again. I think though that had a ship crashed it should have done damage to that pillar and is odd it wouldn't hit one of those buildings. This would take care of my concern about Elf spaceships crashing into the palace as well. It might also mean that the ship that menaces and then crashes into the Asgardian palace is not necessarily the Dark Elves ship. Could easily be more than one realm has a problem with Asgard, in fact clearly more than one does considering the Bourne Woods battle.
In any case, I suspect that the report on set that someone said it was a spaceship may have been an incorrect assumption by someone, or the crew just trying to give onlookers something to get them off their back. LOL... I think it could very well be that the upheaval is the result of the portal or doorway opening to the Elf world and then they come out of that chasm that goes right down the PM line. That's my theory at the moment anyway... And in that case, they could come back through the portal more than once, certainly especially if they gain the technology, and/or a person who has knowledge of the technology to make it open again.
I think it's possible that Kurse could be in some of the shadow boxing stuff we'd seen there, yes.
Here is my current speculation for the beginning order of things. Don't ask me how many acts I have here exactly because I have no idea. LOL
According to the Italy footage review it was said that it starts and end of Earth, so first we see Jane and co working on portals on Earth, and maybe touch on her being disappointed/sad that Thor did not return, and trying to move on with her social life... etc...
up on Asgard, Loki has been sentenced to prison, and there is a bit of discussion with Thor Odin and Frigga over that before either Thor or Frigga or both visit Loki in prison and tries to get through to him. But he's very angry and distressed and getting more and more "bag of cats"-ish.

After they leave, I thought it could be interesting if Malekith gets in contact with him trying to strike a deal to help him get out and get revenge on Thor, so that might be a time for Loki to tell Malekith about Thor's interest in Jane. Though this is not completely necessary since the Dark Elves could simply be aware of her due to her research on portals, and not necessarily to do with Thor. But I think it would be an interesting bit to add, and give Malekith all the more reason to see how he can use Jane to his advantage. I might be tempted to keep that a secret betrayal to be revealed later if I were writing though.
So then some time passes, and maybe on Earth we get a sense that something weird is going on around Jane, Erik, and Darcy. Like Malekith is manipulating Jane to do the research there specifically at Greenwich U. for a reason, or an imposter is in their midst manipulating, or something like that... (in the comics one of the DE's pretended to be Lorelei to get to Thor, so they may have this shapeshifting ability in the MCU as well, not necessarily one of the main characters).
Up on Asgard...Thor is finally to be made king, another big ceremony is being planned, but not all the realms are happy about this, such as Vanaheim (including any demons and trolls also living on Vanaheim with the Vanir), and they are plotting, possibly with Malekith to stop it. They know ceremony for Thor is being planned and they must act before Thor is crowned or the fear is he'll be too powerful for them to defeat if he's given the Odinforce. The plan is to attack at the same time and cause the Asgardians to spread themselves thin, and make them easier to defeat.
The ceremony for Thor to be made king is about to begin.
Jane and co succeed in opening portal at Greenwich U and what comes out from the other side is not good. (Dark Elves and Malekith)
Elsewhere on Asgard, they are invaded at the same time (Bourne Woods)
Heimdall sees all this and hurries to tell Odin and Thor interrupting the ceremony, giving us a bit of a "not again" moment, which I think would actually be a bit of a funny moment. They needs some humor I think if the rest is going to be so "dark" and I think if it's done with a bit of humor that it wouldn't seem so much like they are doing the exact same thing. It would have a different tone to it. I just think it could be a funny moment and it fits well into my outline.

Plus the audience will see the attacks coming so it's a bit different than in Thor 1, they'll be expecting a "not again" humor moment. LOL
Thor insists on going to Midgard to defend them from the Dark Elf attack, Odin isn't happy as it seems he's more concerned with Midgard than Asgard, but sends him anyway, figuring they have enough warriors to fight off the Asgard attack. Odin sends Sif and Warriors 3 and many Einherjar to the place of the invasion/Bourne woods scenes to fight that threat off. Odin stays behind at the palace with Frigga, in case the palace needs defending as so many Einherjar need to go to Bourne woods. It's my feeling that they may think the Vanir are not that much of a threat, and that would go along with the mythos and the game I mentioned that the Asgardians don't think much of the Vanir as warriors at least.
Unbeknownst to anyone, a ship, cloaked even from Odin and Heimdall's gaze appears, with Dark Elves and led by Algrim, and is headed towards the palace.
Thor fights Malekith and the invading Dark Elves on Midgard, and saves Jane and co. Malekith escapes through the portal and Jane closes it behind him with her little doohickey she carries around.
Sif and co fight on their own in Bourne Woods.
The palace is crashed into by the Dark Elf ship, and they attack the palace. Frigga is dealt a fatal blow, possibly item(s) are taken from Odin's vault before the invaders escape. (possibly the Tesseract, or possibly another item that might make Malekith more powerful and change Algrim into Kurse if there is one)
On Earth, Erik, Jane and Thor sort out how to open a portal to get back to Asgard, he brings Jane with him, either for protection (in which case he'd bring EriK and Darcy too) or just to make things up to her.
Thor returns and finds Frigga dead or dying, and Odin heartbroken. Before she dies Frigga makes Odin promise to find a way to help Loki back to the family and to redeem himself as she loves him as much as she does Thor.

Any annoyance Jane might have had at him for not coming to see her quickly lets go as she can see he needs to be comforted in the wake of his mother's death. That moves that relationship forward quite a bit rather quickly (not sexually necessarily just emotionally I mean). Thor perhaps feels some blame on himself for this for leaving Asgard, and then realizes his friends need him in Bourne woods and so he goes off, and maybe Jane stays behind with Odin.
Sif and co have more on their hands with their fight then first thought, and Thor arrives to help fight those invaders off. In the notice about those scene from the studio, it says the two kingdoms are battling and the hero comes to save the day, so it could be that Thor does not come with the rest, he could show up later. It would be good to see Sif and the others fighting without Thor too. The cost is great for the Asgardians but they manage to send those invaders packing as well.
This is a bit more fill in the blanks fan fiction here but bear with me. The remaining warriors return to Asgard with Thor, Thor learns from Odin that he believes Loki's past connection to Vanaheim (due to having been trained in sorcery there during more peaceful times) could help them achieve a truce with them, and get reinforcements needed to defeat the Dark Elves. Thor doesn't like this idea but Odin insists that he may be able to help them come to a truce with them (which is also a plan to give Loki a shot at redemption, per Odin's promise to Frigga before she died). Once they come to a truce with the Vanir they can get them to combine forces with the Asgardians to then take down the now greater threat of the Dark Elves (who not only killed Frigga but took something dangerous from Odin's vault that makes them dangerous to all the realms). Thor has to go visit Loki in prison, tells him about Frigga's death and offers to give him a chance at redemption if he helps with this truce with Vanaheim. Loki agrees. If Loki is the one who tells Malekith about Jane and Thor, he might realize at this point that if Thor hadn't been distracted trying to save Jane and Midgard, that Frigga might still be alive, and so that might be part of why he agrees to help. (though he certainly won't tell Thor that at that time at least...)
The defeated Vanir are angry with Malekith and the Dark Elves that they did not kill or keep Thor distracted as they said they would, and they perhaps feel betrayed, and possibly even manipulated by Malekith. So that opens up the possibility to the audience that a truce may be possible against the Dark Elves. And perhaps Odin also suspects that Malekith manipulating them to get the items in the vault was what Malekith has in mind all along and not necessarily that they would defeat the Asgardians with the help of the Vanir. They are pawns for Malekith (and possibly whoever may be backing him, if he's got another big bad like Surtur or Thanos working behind the scenes in the shadows)
that's all I've got for now...
edit: at the moment I'm thinking time-wise that Thor going to see Loki about helping him would take place at about the same time in Thor 1 that Thor finds himself on Midgard hit by Jane's vehicle.