Also wanted to add, if you wanted to keep the weapon-aspect of Starkiller Base, you should be able to trim the Resistance briefing to remove any mention of the shields. You possibly could use a shot of 3PO, and possibly come up with some dialogue, where he says something regarding the map after they have discussed the Oscillator, like, “And the map?”. Han looks at Finn and says, “Kid?”, then Finn says something like, “I can do it… but I need to be there, on the planet.” Han, “We’ll get you there.”
So Finn, Han, Chewie and Black Squadron would sort of have two separate objectives. Once Han and Finn get the map (or don’t) Black Squadron comes in to blow Starkiller up.
I think I personally prefer the idea of it not being a weapon, but I think another challenge of removing the weapon aspect would be creating shots for the First Order fleet attacking Hosnian Prime. I think it is possible to reuse and manipulate certain shots from TLJ to make it work (maybe even include a shot of Captain Cannady saying “Fire” or something).
Not only that, but it also needs to feel cohesive with the everything going on at Starkiller Base. With Restructured, at least blowing up Starkiller is tied to saving the Republic. If they don’t destroy it in time, the Republic is destroyed.
In my suggested version, the fleet leaves to prepare for their invasion before the Resistance mission even starts, and their only objective is to find Luke. I think we could see the fleet leave Starkiller right after Hux gives his speech, but we wouldn’t see that fleet again until they arrive at Hosnian Prime to destroy it. Even then, if we cut to that right after Han dies, will it have the same impact?
You get what I’m saying? They are sort of disconnected. I mean, they want to get the map to find Luke because they think he can stop the First Order, but this makes the Resistance feel like they’re two steps behind rather than just one. On the other hand, another benefit of the Fleet idea is that it would explain why Starkiller feels so empty when the Resistance arrives. And you could argue they are still tied together, since Hux can still decide in this version that they must attack the Republic AFTER the Resistance gets the crucial piece of the map, a step closer to Skywalker. Maybe a shot of the Star Destroyer(s) in hyperspace could be generated to intercut during the Starkiller battle. Maybe one of the pilots could jokingly say, “Where is everybody?” I guess the key might be to have a moment or two that reminds the audience that the fleet is on its way, and to create tension. Possibly redubbing that Resistance alien officer to say the Republic is assembling their fleet to help.
If it really couldn’t work there, you could possibly move the Hosnian destruction back to the second act (but keep what Restructured has, where Kylo’s Star Destroyer is above Takodana.) The only downside is that you would lose that deleted scene with Kor Sella and Leia, losing more political context in the film.
I really think the First Order fleet destroying Hosnian Prime would be a really cool sequence though if we can just figure out the structure of it.
Also, if we see the Dreadnought’s destructive force in TFA, it makes the battle of D’Qar feel more important because we know what these things are capable of.