Realize that the derailleur has a second purpose. It is a chain tensioner. When the bike folds the spread between the Front Sprocket and rear Cogs shortens. The derailleur takes up the slack that would otherwise be created.

The Jifo is a single speed on the same design principal. It requires a separate chain tensioner for that purpose.

I am quite sure it would be very difficult to fit an Internal Gear Hub in the 76mm OLD. I believe you could play with the sprockets back there however I believe. You can't really do that w/ an IGH other than changing the front chainring, which you could do, likely anyway, with the EEZZ and Jifo.

I like IGH hubs too so no disagrement there.