I think the PI-like area isn't viable any more. I think the days of closed off adult only sections are over.
While Disney obviously isn't concerned about the demographic, I think there is a demand for adult only venues (not admission gated areas) after a certain time of night.
Disney really needs to go upscale though. Church Street and Uni have their demographic. Disney should look into gastro pubs, tap rooms, and wine bars that are open until a reasonable hour to the general public then are closed off to the under 21 crowd.
Having been a CM, I can understand Disney not wanting to cater to that crowd. We were cheap.