I like the concept, but the problem with this idea seems to me that you have customer expectations, not owner expectations… Dealing with the public, day in and day out, is not always the social, friendly, relaxed interaction you are imagining - they are sometimes rude, careless, dismissive, and so on. I’m unclear who much you’re joking but I wonder if the reality would be anything like what you imagine it to be…
Musically, I think you really have 2 choices - you go for widespread ambient sound, which can be the same volume (low, or high) all over the room, in which case you need either a series of things like Muso cubes or similar, or an AV amp driving multiple in-ceiling or in-wall speakers (or on-wall).
Or, you go for a more focussed music area at one end, with a stereo speaker pair, and people choose their volume level by where they sit. I’d then be looking at a decent PA/performing music kit for its rugged nature and the ability to play loud as needed.
I’m not convinced that the subtleties of hi-fi are needed - good music, for sure; flexibility in what anyhow it’s played, yes - but the presentation will be echoic in the space you describe, with loads of ambient noise and chatter - why spend money on things that are not well suited to that space.
Sure, generate a vibe by having a specific sound - a very valve-oriented approach would be good, with some glowing tubes on display (if you can do it without then being jostled too much) but only at moderate cost - the additional money for high end gear is not really going to be noticed.
And if it’s Ireland, I’d look at two other things - local custom, and visitors. University town gives you potentially all day and all night custom with loads of medium-spending people; quiet country gives you some evenings and more connection with locals. If on tourist route/hotspot, revenues and rents are higher. Many pubs I went into when I was there had a good local music scene, some making it band-friendly (and for turn up and jam sessions) the PA route might be a winner…
All IMHO, obviously.