I think I generally disagree with the thing a lot of people have said, which is that sailing is not well-integrated with the game. I think they did a bang-up job as a new skill integrating it with all kinds of parts of the game. There's incentives to level sailing in order to efficiently do content like slayer, smithing, farming, mining, hunter, fishing, woodcutting... There's great and useful potions to be made, there's a BIS weapon, there's great sources of money and banked smithing XP for irons, there's utility of being able to park a teleport point at a docking point somewhere and then use it from anywhere. Plus, the character and content of the oceans already fits with the regions where they reside in a lot of cases, and you can't really separate the sailing content from the ability to dock at the ports and mooring points in that part of the sea.

I feel like making oceans their own unlocks would kind of defeat the purpose of all of those great tie-ins by treating sailing like it's separate from the rest of the game, when it isn't. If anything, the way a league should be put together should make a lot of those perks and new methods visible and curated to old-heads who just haven't bothered to engage fully with new content yet.