I finally have all the parts I need, so I slapped it all together. I put it on the ancient Taprite regulator I use for my garage keezer and general CO2 stuff.
Back in the Mesozoic Era, when I bought the regulator, my friends down at the Water Buffalo Lodge told me to use fat silicone tubes for gas, so I did that. I made my own 3-hose manifold from Home Depot and Ebay junk.
Today I removed the valves from the manifold and installed ordinary check valves with male flare threads. It goes manifold-check valve-Duotight-EVAbarrier-inline regulator-EVAbarrier-Duotight disconnect. I made one hose extra long so I can pull it out of the keezer and shoot gas into things.
I spent a lot of time holding things under water and spraying joints with sanitizing compound to check for leaks. I gassed up my two garage keezer kegs and then shut the tank valve. If the keg pressures are zero tomorrow, I'll know there is a bad joint. If nonzero, things may be okay.
If the inline regulators work, they will save some room and give me flexibility.