Though I see they have an autocover in the picture, I would not recommend having that sharp corner which the cover will have to drag over each time it opens and closes. Not to mention when it rains and you forgot to put the cover pump on, the weight of the water pulling the cover down will surely stress that area more quickly, and lead to a premature tear. Ideally, I'd find a design way to round off the outside edge of the entire spa. Perhaps a stone mason with real talent could do it with some thick PA bluestone, which is what the picture appears to be show. Any raised spa will also impact the cover operation though they can certainly be done.
As a side note, the bluestone coping on that pool is fairly thin, probably 1 - 1 1/4" thick (the same as mine). Though at first glance you may want thicker (and give consideration to if you want the thermal treated surface variety), the downside to thicker with an autocover is that the deck level becomes much higher than the water level. The integrated autocover rail adds about 1" above the tile, then 1/2" or more of grout then the coping. If you want to see some closeups of this scenario, see our build thread, the link to which is in my signature.
Best of luck with your project. With that as an inspiration photo, I'm sure it will be great!
Also feel free to document your build, continuing right in this thread, so information all remains in one place. We'd all love to follow your experience - and we love pictures!