I stand by my answer. It might be fun to some people to entertain an amount of raving lunacy, but when shove comes to push, you need technically sound answers, and implementations that work. The tradeoffs about these kinds of subjects and architectures were mainly done in the 60s and 70s, there's little honor in straightforward tradeoffs about cache schemes and basic policies, and there's statistics you can do on that, incorporating bandwidth considerations that can work, but are limited in their true analytic and practical value. It's fine to talk about, but there are other reasons for the way things are.
Engineering time and cost, testing constructs for which there is no good (kernal) software, and in the case of the3 Parallella, there's the proof of making a low energy machine with good educational value.
Redoing electrical engineering from the 80s about computer architecture is nice, but that game requires you yourself play too, so, make something ! MIght be fun.
T.V.