Earlier quoted context omitted.
The best way to do that stackable staves: see the last two lines here: http://i.imgur.com/tqZRXzt.jpg Ledger lines preserve the melodic contour but it's harder to read the notes. 8va's stay within the regular five lines you know how to read, but fragment the melodic curve. This way has the advantages of both the above and the disadvantage of neither. (The lack of key sig in that image is a limitation of the software…
That's cool, I hadn't played any piece that uses the stacked staff (to my recollection anyway; it's been a good 15 years since I was actively training). It does work better for when the melody progresses into that range, true, but I think it's a "right tool for the job" situation. Often 8va's are used for when you want to raise a single note or chord one time, and that would be much more readable than a separate staf…
That double treble clef is called the super-treble clef and I've only ever seen it in the appendix of a book called the science of sound.