The pressure vessel is the hardest part. I think the idea of a corny keg is a good one if anyone can figure out how to convert the post threads to garden hose. I suppose you could try removing the poppets and clamping hose directly over the posts. It should work up to a certain backpressure. Here's what I found on keg thread:
...SNIP...
It gets a little silly though to sacrifice a corny that's able to hold pressure. I have one that's a little bent where the Oring would engage so I wouldn't trust it for CO2 leaks and I don't mind if it squirts a little water either. Maybe I'll give it a try after I verify that I can't persuade the lid to seal better.
This link mentions
Re: Threading Female Pipe onto a Corny Keg Post Thread?The threads are unique, they are not even close to a National Pipe Thread (NPT) at all. I'm a machinist by trade. I can't even find a standard tap this size (19/32- 18).using a npt fitting will ruin your existing threads. I would suggest using a ball lock or pin lock fitting depending on your keg, with a short piece of tube and then what ever fitting you want.
I tried looking for 19/32 female BSPT ( British Pipe Threads -- Tapered ), but no luck yet.
FWIW, some garden hose quick disconnect fittings that were laying around snap onto posts. At first, I thought the reduction from the hose through the poppet opening would kill the flow rate. But that opening is just about the same diameter as the dip tubes.