For more serious suggestions, I don't have too many...
- The little tips at the end of your inkling's hair? Let the color for those be changed. It would be such a fun little customization thing to let you do that instead of locking it as blue. You know it's fully possible within the games because of Side Order.
- More open maps. Obviously. I don't need to elaborate on much here. The one thing I can say is that I don't mind maps being more closed for the sake of forcing at least a little bit better coordination...if and only if we're talking about Turf War. Maps should see dramatic changes in ranked modes if you want to take that approach. Something I will say that has not been talked to death though...
- Drastically improve the spawn areas of each map. Museum gets incredibly close to what I'd hope for here. The top left route and top right routes are both incredibly difficult for attackers to get to, although still possible, and give ways of dropping into mid that bypass anyone trying to spawn camp if they're not coordinating well enough. Yeah this is mostly a fix for the more casual side of things as opposed to anything that's messed with my experience but very often you'll see waves of online complaints about spawn camping. I think the range of movement you have with your spawner should be increased and maps should use Museum as a model, although in my opinion top right should not be accessible at all for attackers.
- ...Really other than improved netcode and maybe like the pvp Pearl Drone stuff, all I'd especially want is for my main to get a unique kit to play with until second kits roll around, not necessarily even a good one. I'd hope that one of the two is good but if I get like Splash Wall + Reefslider on Decav for example it'd feel way worse to me than if they gave it Sprinkler. Splash Wall would be one of my favorite subs this weapon could have, but its existence here would make the whole package just feel like a worse version of Splatoon 3 Charcoal Decavitator. Would I prefer a better kit that makes me wish I was playing something else or a worse kit that gives me new things to learn and work around? The choice is obvious.