I agree that UPL has some promise. The rule-set is pretty good, the shot clock helps, moreover, the co-located events or juniors, women, amateurs etc. are an avenue to bringing casual APA types in as participants and fans.
I really think focusing on in-person fan experience would go a long way. Golf is much harder to follow as an in-person spectator than pool, but attending golf tournaments is awesome, and attending pool tournaments isn't something I'd currently spend much to do. A hybrid experience with real-time brackets, scores, and key matches on screens throughout the venue would help. Hospitality options would be good. In the US, pool is a bar game; getting some appropriate booze sponsors should be easy work, regional food options would be cool. Buffs is in one of the best food towns on earth, Vegas has great food, maybe try and get some of that featured to fans and participants. Some premiums spaces, maybe with player interactions, clinics, premium viewing, would all be nice. Equipment demos, fan challenges and games, maybe a premium cigar and whisky experience, could all make attending events more fun and feel more premium, without excluding the core pool demographics.
NASCAR has awesome hospitality options that are approachable for their fan-base and also very premium. 8-Ball pool could too, just need to make it a priority.