There will be seafaring to some extent. Fishing was long request in Bronze Age 3 that I never got around to, but the new pop system I'm working on would support it better.
Well either of those features could potentially be affected by the Heirs of Atlantis trait. But I'm weary of suggesting too much. I know how bad feature creep can get.
Yeah, totally understand that. I have some other ideas, like a bonus to an archeology system like Stellaris, revolving around discovering and recovering Atlantean ruins. But that's pretty far into the nebulous future.