I've seen a lot of combination pool rooms, the most popular idea being bar/poolroom. That's as safe a bet as any. You also see club/poolroom, with a dance floor and loud music... perfect for serious players.
The thing I notice is that most of the time, the pool part of the business suffers because it's not the part that's making money. If the deli part is successful, it just carries the pool room on its back. When you have a few extra grand to reinvest, will you refelt the tables, or spend it on restaurant equipment, which is your bread and butter?
The only time I've played in a pool hall where the equipment is perfect (which is what I 95% care about)... is in an actual pool hall that doesn't have any secondary business attached to it.
Depending on your area, there may be an untapped market of frustrated players looking for a real pool hall with quality equipment vs. a bar with tables. I personally am driving 35-40 miles every week to play on good equipment, though I can play on garbage 15 miles away.