Definitely mermaid depth. I want a perk/skill/power tree like vampires. Plus some QoL mermaid details. I've always liked the tail showing up in the bath and more stuff like that would be appreciated. I would also be happy with any extra stuff added to CAS, etc. here.
Definitely more water activities and activities in general. I don't have to have it, but underwater would be really nice. Especially with mermaids.
I really like Sulani as a world. It is one of my favorites. However, I agree the culture could use some buffing. I know the festivals were stated to be informal, but if I am resident I should know enough to be able to attend them. I would not turn down a culture skill, but I am not sure that should be the way ago. With residential worlds, like IL's and SE's, I like the cultural differences offered in a variety of ways, rather than it feeling like something you have to learn like vacation only JA. I do not think I like the idea of having a kid just never learning the skill so they aren't a part of it. Kids do learn their culture, but it is not 1:1 like say a skill.
If I can get them, more traits. Always like more traits. I'd like an ocean focused nature aspiration in particular, but any aspirations. I would certainly like a new skill. Also any extra cross play would be lovely.
I do not really have a huge list of desires for IL in particular. Make mermaids better and give me more stuff, especially cross play, and I will be happy.
