I think Dick and are making a similar suggestion. Install a 2x4 or 2x6 across the opening flush with the face of the wall, Paint it white, and install the crown molding. Cutting the inside corner at that compound and could be interesting. You could use the little corner blocks.
Why do your seams fail? How big are the openings? There is a phenomenon known as Truss Lift or Truss UpLift. I can go into in depth detail if you want. Its the bane of the truss industry. I the crack are hairline you can use very flexible caulking to conceal most of them. If the paper is split it can be significant cause of heat loss.