One thing does concern me. Removing the existing ceiling joists could possibly cause problems. In conventionally framed roof systems, the ceiling joists act to keep the thrust of the rafters from pushing the walls out. There are smaller collar ties up higher visible in the photos, but these might not be sufficient to check the forces that will come into play now that the joists have been removed. The original configuration was a triangle, with the joists being the base and attaching to the sides of each rafter right where they bear upon the walls. There are several solutions to this, one being to install a continuous beam at the ridge supported at intervals by posts.
The movement might not occur immediately, but sooner or later, gravity always wins.
