It will be extremely extensive changes for just one truss.
Basically, a new truss must be built and the wall must be reinforced.
The problem is that when the lower chord of the truss is raised, a lot of horizontal outward forces are transferred to the walls, which they are not built for.
In my naivety, I thought it was just a matter of putting in a new lower chord a little higher up and then cutting the old lower chord, I was wrong

Will probably not proceed with this project.