I have had great success with mounting a large 3/4-1 inch good solid board up against the thin walls and anchor in place with MOLLY BOLTs. This will spread out the weight across the large area and you can mount your TV mounts to the that... Dresses up nice and holds up alot weight.
Your idea sounds great - might even be somewhat of an over-kill but if you can do it go for it - alot of folks don't have the ability to get around what studs there is in the walls so if you can find them is always a good idea to use them... Using MOLLY BOLTS is also a great idea.
Mounting the solid boards up first then mounting your TV mounts to the boards always works out great.
sample photos from google images