I really like this idea, especially since we clearly have an adventure park in Oasis Springs with that giant dinosaur in the background. Definitely would be a cool vacation world. I'd like a lot of rabbithole things like in Jungle Adventure but maybe also some activities like in Snowy Escape and Island Living.
Maybe it could update the fossil collection by adding more objects and sort of overhauling it. I don't like it when they pull items or gameplay functions from other packs into new packs but I think the archaeology skill from Jungle Adventure could be used here. Maybe they could take that system and really give it an overhaul. Similarly with rockclimbing from Fitness Stuff.
The only problem I forsee with this pack is that it's not entirely marketable unless it also adds in daily gameplay. I can see it adding in lots of great BB and CAS items but what would it bring gameplay wise? I don't think it would be big enough to be an expansion but maybe a game pack. So we're looking at vacations, recipes, collectibles, and... a new pet? Maybe it could add reptile and amphibian pets, but EA might not want the mesh and animation work involved with all that. I, myself, just can't think of something that would make people want to buy it beyond cosmetics.