Goby, I wouldn't know myself, but it is definately something that one should know before buying the tank. I think some companies cover custom installation in their warrantees, but that might require that the company does the install work. Again, probably not a cheap option, but worth doing research.
The Aquarium Obsessed tanks are amazingly beautiful, but they are not worth the price if you are doing an in-wall. What makes them really nice is their eurobraced and rimless aquariums. But since you can hide the trim in an inwall, it isn't necessary.