Getting a tear-free solution would be expensive (you'd need a frame buffer to store an entire screen), but does it really matter? Compact Macs can't do full screen animation without tearing to begin with! Given the amount of "motion" on a typical desktop, it won't be too noticeable anyway.
This is super cool. I have no horse in this race, can't really picture a use-case for this in my world, and I'm still beyond psyched to read about the concept and progress here, and if it ever turned into a commercial offering I'd almost certainly snap one up just for the cool-factor. Nice work!