Yep, I am on this train. I want a proper swimmable beach. I also want them to be able to lounge on lounge chairs or beach towels without my needing to turn off all autonomy. I get annoyed when they won't sit still or when they won't stay in the hot tub. I don't plan for them to lounge all the time but if I send a sim to do that then I want them to stay there. Yes, tanning, burning and sun lotion could come back. I say that because then I can have someone stay on a lounge chair reading or relaxing while I send other sims to swim or do other activities.
I agree about seeing more water activities and curved pools. I'd also be cool with a cruise ship theme. I did not have IP so I don't know much about what was in it. Anyway, I agree with this and with wanting more cultural activities centered around that theme. There could be steel drum bands, reggaeton music, relaxed clothing and souvenirs. I agree about offering new foods and interactions. There could be the risk of sharks or jellyfish. If they want to keep with the eco theme, there could be regenerating areas for cleaning up pollution.
I think JA offered a good paradigm in terms of offering a variety of housing, adventurous and cultural activities. I've said this before but I would make sure that a beach offers areas for families, secluded romance and a party area. With what we've seen in JA, they could add some adventurous elements as well. I'm interested in both resorts and in the ability to for sims to purchase beach homes. There would be a real fight over owning beach lots in my game if that happens.