No reason to use aluminum for the roof extension. It would be more trouble than good.
However 3/16th aluminum angle would be great for building the roof deck frame. Just be sure to isolate it from the steel to avoid galvanic corrosion.
Super strut is a bit heavy for what it is. It was not made for mobile uses.
I would get some channel formed up at a metal shop from 14 gauge sheet steel. Have them make it to the same size as the original support ribs (channels) in the bus.
If I was you, I would just raise that section of roof, and not bother with all that folding stuff you mentioned. It sounds like a leaky mess waiting to happen.
Center of gravity will not be a issue as long as all you water tanks and other heavy objects are kept low at frame height or lower.
More than one member here have raised their entire roof to 12 feet. The bus body does not weigh as much as you think.
Also, please stay with metal sheeting on the outside. Wood has no place on the exterior of a bus. Think of what would happen if a piece of cedar came off and hit a car behind you. Also the metal is what locks all the framing together, making everything strong.
I'm looking forward to pics.
"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."
Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization