I had an idea the other day, and it was an idea for a mod.

Now I'm not a modder, so i wouldn't know how to do this or if it's even possible...but what if we had "Gravitee" Blocks? My idea behind it is this: You make 4 gravity blocks, place them in a square against a wall, right click them, and set them to the same frequency between 1-1000. Then, whenever you make contact with this wall, your camera flips so that now you're new "down' would be towards that wall. Now if I make contact with another wall with these Gravitee blocks being powered, or touch the normal ground, the camera flips so that that side is now your "down".

Then there can be the "Grav. Correction Tool". Lets say you're upside down on a ceiling or something when you accidentally slip and fly up into the sky. Right clicking with this tool, the gravity will fix itself so that it's facing the normal way it usually is in.

On the issue of doing things like growing plants/trees and placing liquids: Maybe they work by the blocks sensing what it WOULD do normally and applies it in the direction you're in at the moment.
Example 1: You place a sapling while on the ceiling of your dirt home (noob). You bone meal it and it grows as if you had grown it right-side up.
Example 2: You place a bucket of lava/water in a 2x2 square in your ceiling while upside-down. The lava doesn't flow toward the usual floor but flows upside-down.

Expanding on this idea, i came up with what if you built a giant floating cube with the corners being these Gravitee blocks and set them to the same frequency and powered them. I started powering them while I was on top of the cube. Then I moved to the edge, jumped off, AND... Gravitee flipped to one of the side faces! As long as I don't make contact with the another FACE of the cube (or any blocks underneath the cube of which it is floating over), then I'll stay attracted in that direction.

Idk, just and idea... XP