I don't think a dust cap has enough metal to support the force required to remove the crankarm. I'm guessing it would take more than another washer to do the trick. I'm not an engineer though so take my opinion with a grain of salt.

nah, it won't work if the crank is pressed on. The cap is way too weak.

Making them is as easy as pie......for that crank or any other crank. I wish I still had the name of the machine shop in NJ that made my one key releases and titanium Campy axles. I'd ask them to contract a run of TA one key releases and charge you guy 4X cost.