This heat insulation panel will be long term fix. Like one off installation.
I think you can search Re-Roof Service. A lot of local they did this to old tiles roof. Basically they add Tower Support & C-Purlin Bar over the old roof then insulation (EPS,PU or Rockwool) foil and metal sheet roof panel over it. It is easy and very light. Provided your old existing roof are in good shape and condition.
I think this will be cheaper than steel structure and cement roof. If you intended to go for Solar Panel eventually, I reckon to go for Standing seam roof so that your solar panel can mount easily. No bolt, less leakage in the future. Best of luck.