That's awesome!
About 10/15 years ago there was a changing table for sale online called the EZ-Change. It appeared to be marketed to schools, special needs daycares, etc for changing special needs kids and adults. The videos they had of it operating - it looked super neat, but it was clearly a made in someones garage prototype. It pivoted horizontal to vertical - and when it was vertical it had a seat which you would transfer the changee to (or ostebsibly have them sit down themselves if they were capable) The legs of the seat had stirrupy type cuffs with velcro to secure their calves to. You would then pivot the table to horizontal and the person would be on their back, the seat would drop away and the changee would be hoisted up by their legs (almost like lifting a toddler by their ankles) Giving you access to change them, slip a new diaper under them etc. The demo video showed a very petite small woman help a kid transfer to the table and 'change' him with real ease. The leg cuffs and stirrups were constructed from PVC pipe - and they had applied for a patent (I have had no luck turning up the application either) - I really feel had they have had a more professional web presence (the site was very geocities for anyone who might remember what that means) and the product clearly looked homemade instead of like a real piece of medical equipment - had they have had a better more polished presentation I believe the would have met with much better success. I have a picture from their website which was some of the only media preserved (the internet archive / wayback machine sadly did not capture the flash video and flash photo gallery - which might have given more clues on how to reconstruct one)
The company sold both the plans and completed tables, and I have searched and searched hoping to find them, as I think there are a lot of us would like such a contraption, that gave the whole being hoisted up by the ankles experience.