Vertically-oriented slime-themed Dimension

I've found it strange that all of Minecraft's dimensions thus far are flat planes. I think an additional dimension could be more unique by having infinite depth with finite X and Z coordinates. Naturally, a good theme for a vertical dimension would be slime, since that would cushion players' falls. It also provides a better source for slime than current methods. Different colors of slime could also be featured and it could be inhabited by slimes and more mobs belonging to the slime/magma cube family, as well as frogs. With its height this dimension would also be perfect for making dropper minigame maps.

Lore wise, I would imagine this dimension as being the space between all other Minecraft dimensions, but instead of an empty void the realm is filled with prima materia waiting to be molded into new worlds. Lately features relating to the lore for Minecraft have been sort of dreary, so a colorful and whimsical dimension could be a breath of fresh air.