Last night I had a dream that I played a mostly-complete very-playable version of FEZ II.
Since it's highly unlikely that FEZ II will ever be a real thing, and because I enjoyed this vision of it so much, I think I'll describe it here.
First of all, the game world was a five-dimensional manifold; the world map was two-dimensional (seen as an overworld map that had its own cohesive landscape), and each world map section mapped to a three-dimensional slice (which was generally perceived as the four-way two-dimensional "stacked" mechanism from the first game). Doorways and bridges linked the different world map sections together.
There were several different characters that you could switch between. These characters were identified by color, and had different physical characteristics, and this affected the way that they could traverse the worlds. They also had different goals. In the dream I only got to play a few of them.
Many of the puzzles had to be solved in tandem by two characters. Some of them could be done by a single player by switching between the two, but many of them required online networked play. This seemed to be Journey-style, where players were randomly-linked with one another based on being different colors in the same slice.
Orange could only go through hot places safely. It could also swim through water, and could see all of the thermal currents within it. It could also see the spirits of the dead. (One underground cave was filled with water that alternated between fire and ice, and the creatures could live in one or the other, and would die when going into the wrong temperature.)
Black and white were paired up with one another, and had to solve puzzles in tandem (switching back and forth). Their puzzles tended to involve shifting tiles around in space; they had a wand which could create and destroy a limited number of blocks.
Light-gray was a ghost. It could only go up (the "fall" threshold for going down was severe), but it could also go through walls, and could stand on clouds (but these would fall away after only a couple of seconds). Its goal was to get to heaven (which was somewhere above the icy North). Many of the 3D slices would wrap around vertically, as they sometimes did in FEZ. This was the only way for light-gray to go down.
Dark-gray was three-dimensional, and was capable of moving in any direction within the slice (playing it gave you a view much like the 3D glasses in the first game, except third-person).
There were also red, blue, and purple, but I didn't get a chance to play any of them before I woke up.