I dunno, looks nice and all, good idea for the casade heat-spreading, but I have to go with the old saying on Junk-Yard-Wars... "K.I.S.S!" Keep It Supid Simple. The more complex the project, the more problems to arise and the more time it takes to figure out just why or what is causing them etc... But I know, innovation is fun and usually leads to something better from the experience. I hope this block works well... only thing though, with all those connections, that makes for 8-10 more areas that could potentially spring a leak. Every extra connection you have (not YOU) is a risk and more bulk for clamps etc... But again, nice design, wish I had the time and tools to give it a try@!
BTW- I'm not at all slamming your wonderful design, just pointing out some possible troubles, if at all?