What are we doing for those two weeks?
I think yes we need time to plan what is the next stage, but two weeks or more for this seems.... a little long..... I may just not be getting what the time is needed for though.
Attempting assasinations and going to One Oak are good options. Why is Sylvanus completly out now? AB is in control so Bluestar is in control, but underground for pheonix support may not be a bad deal. Eventaully the evil of the west will be gone and it will be us against the bluestar might as well get some more support (Keeping Jansten around and having him as an ally also good for these purposes). With an alliance of sorts set up we also shouldn't have to be fighting in and out and all over Sylvanus.
Plus we could find out exactly what is happening there. It's a big world and we only know about our little area... might be good pre-emptively find out what is going on, instead of as with AB learnign the big news of the times at inopertune moments. This won't end it completely, but more info. more guides.
Building a place to house the spirit blades on another plane could happen while we do other things- but very necessary to start. Once the building is made which may take a while then we go for another blade.
We can use all the collected blades as leverage at the final moment- "hey Blue, tell us how you plan to destroy them. Then we'll go get ours. Just to make sure."