I would agree to build the engine for high-altitude/DA, and let the engine controls handle the fuel and timing for any conditions from there. I'm all about EFI, custom ignitions and tuning, and the up-side is the ability for it to handle your high density altitude best, while also compensating for trips to the lowlands on crappy pump gas. Take a low-DA morning and drive to the lowlands to tune your high manifold pressure areas, which it will never see at higher altitudes, but when and if conditions are there it will then handle it in-stride with best possible performance.
I also would not rely on a system knock sensor, and instead tune using a set of electronic ears (buy or build), as they are much more sensitive while tuning, and the human brain can detect trends much quicker and more accurately than a black box. Coupled with spark plug reading, it's reliable. Once tuned properly, and assuming your fuel grade is maintained at the level used for tuning, a knock sensor should not ever trigger after that anyway. You would not want a system that pushes timing constantly until detonation then back-off and try again over and over. Performance is lower as it's designed to continuously try to cope with different fuel grades, and the timing is never quite right (mostly above or below optimal timing) as it is searching. Tell it where best performance is for your engine build and fuel of choice, and leave it there.
-= If it was easy, everyone would do it =-