Crappy 3D model:

The whole basic idea is to create the most realistic environment for a game you play.
I have only thought of this for first person shooters, or games like Oblivion.
Walking/Running Realism.The main parts consist of the roller, I guess you can call, which is the sphere the human will stand on. It will be able to roll in all directs, but hold enough friction for the human to keep balance. The roller stays in place on the frame, so it may seem like you move, but you really don't. Just like how mice work, this could be used to make the running or walking highly realistic to the player. Depending on how fast you walk, the ball will spin at certain speeds. The speeds will be calculated in the direction it is spinning, and how fast to measure out how fast the virtual player is running/walking.
Stillness/weight Realism.On the side of the roller, a cylinder like piece holds it like a frame. The pieces that come up from it, are also part of the frame. It holds a lightweight suit, or frame for the play to move it, with a balance of weights, to make it seem weightless... if possible. If you add an item to the inventory, or pick on up, the suit could increase weight, for the object picked up. The frame's suit also provides stillness, so when running or walking, you stay in the same place.
Vision Realism.Easy, the classic glasses. High resolution glasses, with the a curve to create a real effect, besides a flat screen. The frame's suit can read your head movements, to move the screen in the direction your head moves. The eyes will be pretty large, so if you look around by just moving your eyes, it'll seem like your looking into a the whole virtual world.
Audio Realism.Thought it's quite obvious and easy, surround sound. Perfect headphones for the perfect virtual reality. Just as some to the suit for more realistic sound. Explosions can trail off into high pitch noise, and cancel out all the other noise, instead of actually making a big enough sound to make your ears ring.
Touch/Pain Realism.Although this is most likely really tough, it is still possible. If you were to have a full body suit, it would be make of metal, or steel, with bendable arm constraints, and everything else needed to seem like it's not their. The biggest and hardest part, would be adding a huge mess of tiny spheres all over the body, inside of the metal, so when you go to touch something in game, the sphere could move and create a texture for the thing you touch. You would also need constraints to hold your hand, or your body from moving farther, so you won't go through things.
Pain can be dealt with, with either real pain, with the spheres hitting you, or tricking the nerves in your skin.
You would probably also have to use the constraints used to keep you from walking into a wall, for making a small boundary for the weapons you use.
This may just sound really stupid, but I just got this crazy idea out of no where.
TL;DR: If you actually care, read. If not, then leave.