Actually the gravitational thing isn't at all tricky, except in placement. The basic unit is the reverse gravity spell, which simply inverts the local gravity in its AoE. Placed in such a way as to have the wall exactly where gravity and reversed gravity intersect you get a point of null gravity.

The biggest cost problem is that reverse gravity isn't on the permanency list, necessitating the creation of magic devices if we stick to strickt raw. I actually have come up with a cost effective way to make permanent spells, but under the strictest definition it'd probably be considered home-brew.

..... RESETTING TRAPS!!!

Holy hell, I think I just invented antigravity in D&D.