@wolfmanbush I think season 15 did plenty for HC. It stuck to its roots while adding plenty of new content and rewards. We'll see how the rest of it comes together, but I don't agree that adding weight or ultra rare fish would really do much. After all the gameplay loop would be exactly the same.
I've made a lot of posts on potential reworks for older content that are doable, would help improve replay ability, and just generally freshen older content up. The one that best reflects my most recent thoughts and ideas are part of a very large rework to guilds, you can find it here (don't necro). Personally I think the game could be improved by incorporating out of game features/tools directly into the game, adding random elements that dramatically shake up gameplay or the experience, and improving PvP to be more approachable and incorporated for all types of players.
First of all, I think many of the tools/features (whether made by Rare or not) people rely on to interact with stuff such as progression, guilds, or reporting should be incorporated into the game. I went in depth on all the features I think are necessary for guilds in that thread I linked earlier, but I'll summarize it here. They should bring in the LFGuild system directly into the game, provide many many tools for describing and searching for guilds, and provide a guild chat with an announcement channel. It'd also be really cool if we could get some way to actually make LFC posts within your guild. Perhaps that could even link to the website somehow so you don't need to be at your computer to do it, and also so people could be notified of it. Another area that should be greatly expanded is progression tracking. Someone did make a tool for doing a printout of all the progression you made in SoT, with stuff like lifetime gold and percentage tracking towards all kinds of things. Like you can see your HG wr (crazy ik). There have also been tools made for tracking stuff like fish. Bringing a greatly reworked and expanded progression menu would be really nice, providing an easy place to look at all the different things you have done throughout SoT. The last thing is the reporting features. They've already started to bring that into the game but expanding that to more effective and varied reporting would be good. This would all just help make all the different forms of progression and stuff much more cohesive, which just makes it easier for casuals to approach.
The next thing I think they should focus on adding is random factors that can affect your gameplay experience, enhancing replay ability. On the WE side, I think they should bring back a lot of the old modified WEs like the Ashen Skeleton Fort/Fleets. They could bring back Fleefs and add a "of Fortune" version of all the World Events that is just harder and rarer, rather than having the CoF rotate to one thing and just sit there. They could add a bunch of other more common modifiers like having a ghost fleet go around a sea fortress instead (similar to that one event quest) or have an ashen winds that always has boiling water and the smoke effect. For the quests I think a similar thing would be cool. Maybe having a rare version of each quest would be cool, like a "Diamond Vault Key", similar to how you could get the BB in the OoS ghost fleets when at max rep. You could also change the enemies that you have to fight or add a small extra part of the mission. Imagine having to fight a siren queen or skeleton ship at the end of a lost shipment quest. Adding these kinds of updates would allow the game to feel fresh each time you play. It would also help create special moments that bring players together, like they want WE's to do, or create memories.
The final thing is just making improvements to HG and PvP in general. They need to balance the game well so that you can actually use whatever weapons you want and not basically be handicapping yourself. It'd just make it more fun for everyone. Also they should add some kind of tdm mode or feature that way the only way to practice a really important skill isn't just boarding boats. Especially with how they crack down on spawn camping so hard. Like if you wanna practice as a solo player what are you supposed to do?? It'd make it much better for everyone because the best players want the variety, the casuals need the practice, and it'd get people off new players backs. The last PvP/HG improvement I think they should make is vastly improving the defending system. This would let people play hourglass and do literally anything else. I think most people are "PvPvE" players and don't enjoy doing 100+ levels of HG that are just PvP. Also it'd help add variety to the naval HG experience without just making more modes (which distract from the core gameplay experience of a 1v1).
All of these just focus on improving the gameplay experience in all different kinds of ways, without changing the core of the content that is actually well done.