I had a brainwave the other day, when I had my post knocker on the loadall, also a 9.5m. You could put a Tee piece in the return line, at the change over valve, just behind the cab inside the chassis (jcb), or anywhere suitable where the pipes come off the boom. Fit a high pressure lever valve to the Tee, and pipe it directly to tank. Then when a one way attachment needed to be used, with a free flow return, then it would simply be a case of opening the valve and dumping the return to tank, thus negating the spool valve
Of course you could do this on an Excavator, but this kind of thing is already in place I would think?