Idk how you even advance dramatically from ToTK. You either scrap and build from scratch or polish what’s here with small tweaks.
A new setting might do it.
For example, revisiting the Wind Waker idea with a flooded world. You keep the systems-centric approach, only now wind and wave physics are the new hotness. AC4 ship to ship combat by way of Nuts and Bolts.
You could make underwater exploration a big part of the game too, and even time travel. Scuba your way down to a drowned city, then activate the time crystal or whatever to find yourself in the midst of a bustling metropolis.
You could even bring the Majora's Mask time limit gimmick back into play. Finish X, Y, and Z before the waters come. And as you save people, their older selves/descendants appear on the surface islands and they may give you hints on where to go next/what to do.
...so, TotK meets Wind Waker meets Ocarina meets Majora's Mask. This is starting to sound like the videogame equivalent of Homer Simpson's dream car. Lol.
