Well I had been thinking about this for a day.
Best suspension- Hydrolic Piston type, the hydrolic piston is attached to the axle of the wheels, channels built into the sidewalls of the rig is were the hydrolic fluid is stored, underneath the rig there would be an opening for a hydrolic preload damper (for specific weight classes) that can be sold seperately. The way this suspension is, if you get the preload right, you can also us it as a springboard for some sweet move skills.
The wheel - specially designed Kevlar Rubber compound, the compound would be more Kevlar based then normal to reduced moving friction (Allowing all sorts of cool slide and burnout tricks) this also catters to less wheel wear as the kevlar is way more impact resistant and can absorb high amounts of energy. (alot of standard car tires are kevlar/rubber) the tires would be air tires, but would not be adjustable, they would come from the factory with air in them, sealed on to the hub of the wheel. The air volume of the tire wouldnt be much, and the psi wouldnt be insanely high either, prolly 15psi. This would act as a secondary suspension, letting you fall from pretty rediculous hights(when combined with the right preload damper for your suspension.)
The Engine- right now with current tech we cant really do it, but if you wanted to try. the hub of the wheels is about an 1.5 inches thick and 3-4 inches in circumference, that would be enough for a motor and a small High discharge battery. Turbine style vents on the side of the hub provide cooling. Now, on electric cars of this day and age, when they go foward without being under power (Meaning the motor is not recieving electricity) they do something called regenerative braking, this is the bad ars part that solves the power problem. The high output burst power battery with a burst charger and regenerative braking. Now you have infinite power. 1 stroke power assist, 2 strokes recharge. The low friction wheels help with the power too. The turbine type cooling spinning at a decent rate combined with the 2 recharge strokes = low or no heat. For activation you could use the damper set at a certain spot or just use a liquid type pendulum switch to activate the power assist.
all this makes the Air Trek (If you built it with high res components, not elcheapo homebrew) about the size of an AT in the manga, and there is no reason why it wouldnt work, if I had the money, I would build a prototype for you guys. Sadly though, Im just a lonely manga reader with an eye for engineering and design. :P
I have the gearing setup mostly worked out (for the inside of the wheels) Dont ask though, I dont feel like explaining it rofl