What is best way to reinforce shed structure (apart from demo)

This shed is approximately 11 x 9 and was poorly constructed. It resides on gfs property. It should be demo'd but for time being (has stood for at least 10 years in Nova Scotia Canada) it needs reinforcement. Recently extra weight added to roofing and there is a dip in roofline. Please see pics.

The key flaw in structure is that walls and connecting rafters were not attached properly. There are neither ceiling nor floor joists. The rafters merely connect directly to studs with brackets. Key challenges include: because of way constructed, it would be next to impossible to add ceiling joists unless existing structure removed.

As mentioned, it should be demo'd but for $$ reasons she prefers delay that option.