Yeah, this has been frustrating waiting for Ford to fix a problem they caused. I'll probably avoid anything with Sync in the future due to this nonsense. I was finally able to downgrade to 4.4 after finding a Good Samaritan who was posting videos about "siri works after downgrade to 4.4". File links are in the comments. They look generic because they worked on his F150 and my Fusion, both with Sync (no MFT). Had to Master Reset before Install Application but the downgrade took. Now Siri works again through bluetooth after long hold the iphone button.
No need for workarounds that would be dangerous while driving.
Ford Sync, you had one job.