Would you buy one for $20? It wouldn't get used more than a few times a year at most.
I just whipped up a prototype and yes, it works. I lifted my 200cxw/ forks in the air, let it hang, and killed the engine. Then I disconnected the green/FEL lift line (which was difficult but possible.) Trying to reconnect it was completely impossible. The pin felt like it was welded on; it was so stiff. I put my doohickey on the fitting and easily sprayed HyGuard all over my tire and across the driveway. I didn't bother bleeding *all* the fluid out - I blocked up the forks, bled a little more pressure and reconnected it easily.
This prototype is somewhat dangerous. You can inject yourself with hydraulic fluid pretty easily when dealing with that much pressure. Be careful if you muck with pressurized hoses.