Here dwarf pomegranates are common in nurseries, but just as ornamental purposes, fruit as you said is small and in the best case insipid, in worst case downright acidic.
I have a small hedge of dwarf pomegrantes that are about 30 years old, but they aren't even 2 feet tall. I attempted maybe once to taste the fruit but never bothered since.
I have bought the plant i used for this experiment from the nursery, so i cant' really comment on it. I kept it just for few days before grafting. It had maybe 2 fruits, big about as golf balls.
The clone i grafted on is an heirloom variety, planted by my granpa, don't know the name. I have a limited experience in pomegranates, but all the people of the neighborhood say that this clone is actually very good, and since i enjoy it too (fruit sweet with just a little tannin tone) i'm interested in reproducing it. The fruit aren't very big, i would say they are orange sized.
If this methid could keep the plant at dwarf size, it would be great. Considering the size of the stems of my 30 years old dwarf pomegranates i would say that if this works, you could expect a full sized pomegranate at 6 feet tall max without pruning. IF this works: that remains to be seen.
I'm not the best grafter and pomegranates have been around for a long time; looks impossible to me that I’m the first one thinking about this, so my conservative guess is that this at some point doesn't work. Compatibility issues is my guess.
However so far so good, so let's see how things develop.