I think I mentioned this before, but I thought about it more. Being able to expand the equipment grid would be nice. Currently it's 3x3, to be able to go to 3x4 or even 4x4 would be cool.
But would the increase be universal or per character? If it is universal, then the extra squares should be very hard to acquire, maybe every 100 Outerworld levels, 25 Tower levels or something similar. But if they are per character then they could be similar to a Soul Room both in rarity and price.
A similar expansion would be possible with the orbs. The obvious way to go would be a pentagon and then a hexagon, but there is another way of doing it,
You start with a second set which can also max out as a square. Then both squares could join as a cube with four more connectors.
Just ideas. I think the Equipment grid idea is easier to work with. The Orb cube would be too powerful.