The introduction of Quadratum in Kingdom Hearts 4 could be the perfect opportunity to give Sora a home base that can be returned to and customized throughout his adventure. Considering the way that the series has struggled to make a compelling hub world to frequently visit, taking a page out of Disney Dreamlight Valley's book could be the best way to make Quadratum stand out as a central location to this latest title.
Many of the building blocks for a customizable apartment or house are already there in previous games, if Kingdom Hearts 4 doesn't mind pulling concepts from its own Gummi Ship designs into a personalized home for Sora. Combine this with the crossover of fans who have invested time in both the Kingdom Hearts series and Disney Dreamlight Valley, and a connection between these two crossover titles is bound to be a hit.
A Customizable Quadratum Apartment in Kingdom Hearts 4
While it isn't entirely clear how much time Sora will actually spend in Quadratum, an entirely new realm should be more than an opening location. So, if players are going to spend some time here, then it would be worth the effort to let Sora decorate the new apartment he seems to have woken up in. This would be a heavy improvement on the location's design, since the little shown of Sora's apartment in the Kingdom Hearts 4 trailer gives an impression of a very minimalist living space.
This minimalist look is also the case for the start of Disney Dreamlight Valley, as much of the valley itself and the player's house are undecorated at the start of the game. However, for Dreamlight Valley, designing the area to the player's preference is the majority of the gameplay loop, outside of completing quests for various Disney characters. In that same vein, Kingdom Hearts 4 could make sure to keep the gameplay loop centered around heading out from Quadratum and returning after a successful mission, with new collectibles gathered to decorate the apartment along the way.
The result would be a design that would kill two birds with one stone by giving players a reason to return to Quadratum in Kingdom Hearts 4, and allowing players to personalize their individual playthroughs. On the flip side of this design to compel players to return to the hub world, those who don't care or aren't interested in customization would still be able to just set out to the next Disney world with no real delay. It would be all upside, and could even pull from one of the Kingdom Hearts series' longest-running mechanics to give players complete control over Sora's new home.
Customize Sora's Apartment like the Gummi Ship
Although the Gummi Ships in Kingdom Hearts are certainly a divisive topic among fans, Square Enix has put a considerable amount of effort into fine-tuning the systems in place for the Gummi Missions. This has led to Kingdom Hearts 3 not only having the best missions and Gummi overworld in the series, but also the best ship customization by a wide margin. Between unlockable skins, color pallets, and flashy decorations, players can build anything from a motorcycle that flies through space, to a pirate ship, to even a house. Some of which are design blueprints that can also be unlocked.
Putting that level of customization might be difficult for a hyperreal world like Quadratum, which appears to be heavily based on Shibuya in Tokyo. However, this could be exactly where the Dreamlight Valley inspiration comes in, with less of a Lego building block style of customization, and more of an interior design/civil engineer simulator. Players could then collect furniture and home decor from across the various Disney worlds and use them to decorate the living space, as opposed to completely rebuilding it from the ground up.
Kingdom Hearts 4 is in development.