Still feels like a lazy way to just bypass a lot of the character development Eren and even Bertolt have went through. This is why I loved what Armin did to Bertolt during their confrontation when trying to get Eren back. That little conversation about Annie means Bertolt will never forgive in till he sees her safe and well. I also don't see the Survey Corps ever letting Annie go willingly and there are really no other characters besides Reiner or Bertholt who are capable of saving her.
There is a definitive arc that has been setup with Annie as the conflict of interest. SC isn't just going to let her go, and RB want her back. I don't see a partnership ever forming in till this is resolved to some extent. Here are three ways I think it might be finish
Reiner and Bertholt try to broker some deal with the Survey Corps. Unless the Beast Titan personally comes crashing down the front gates of Wall Rose with an army of titans at his back I could never imagine a deal where the SC willingly lets Annie go. Also this choice is really fucking lame and such a pressure release for all the built up drama that has been happening between RBA and SC.
Reiner and Bertholt actively seek out Annie and try to rescue her and in the process most likely killing even more Survey Corps / Military Police members.
They forget Annie exists and she just rots underground. (Doubt it)
Option 2 seems like the best climactic end to it. Bertholt also being killed in the process seems like the perfect end and a really good finish to a redemption arc. I also expect a partnership for the greater good would require both parties to put aside personal grudges. Because right now it has been humanity that has been constantly getting shitted on, and to expect them to forgive and forget (even temporarily) is the definition of trite. I wan't my partnership to be mutual and not some messed up one sided relationship.