Well Norfolk, you know my take on DO. I believe that a familiar concept would make a great niche force, an economy of force screening/delaying force that would be in one league with other specialist light units like mountain, airborne, marine (actually, I think airborne and mountain should be one branch, but that's another topic).

The technological challenges for Do can't be too great - most necessary equipment will be/was developed for the U.S.Army (FCS subsystems) anyways.
I believe that the personnel selection, training & morale effort is much more a problem.

But I'm pretty sure that this didn't "kill" DO either.
I remember very well the report about how an entire 4-man sniper detachment was found slain in Iraq.
DO is probably politically not feasible.