Tip: Layer 3 backgrounds and tides disappear when you hit a message box, so plan your level around that. For example, you can add a sublevel without layer 3 at the start/midpoint, and include your message there.
I did try doing the TRB to remove the controller from jumping, but due to a sequence that the game runs the routines, it performs a check if the player presses jump, then set y speed and sfx before going to the uberasm code during the 1 frame the player lands on the ground. Not to mention, disabling the control also disable flipping as well as jumping, which you don't want.
Well, eventually it was going to be done, and by who else but GreenHammerBro? With use of MarioE's Reverse Gravity patch (Although that does have a few issues, although maybe GreenHammerBro could fix them, although we'll just see), I can certainly say that this indeed is very impressive, although it likely has its bugs, I'll have to test it out.