I don’t know about DNxHD… some people say it works properly but FCP just cannot read its 10 bit. What I can see is when you open files in AE with 16 bits and correct the color shift using 16-235 color range instead of 0-250, quality is not as good as I expected.
(To open DNxHD.mov files in AE, just disable sound of the file using QuickTime ; it works with AE CS5)
Fact is that you’re completely right when you say DNxHD is unusable on FCP (and I would add on PremierePro also).
What I would see on the Shuttle is ProRes !!! They made it on the Hyperdeck Studio, why not on the Shuttle ?