OK this is just the sort of really sick thinking that gets the ol' creative juices flowing, and adds to my already impressive driving record.
Go here and watch the videos. Pay no attention to the result of too sharp a corner on a soft pasture in the first one, we're talking genuine mad science here.
Gotta have one, right? but as they appear here, they're not all that practical, unless you own a horse track.
Consider this variant: You build the chariot pretty much as you see it here. You use real wheels and tires, you know, like street legal, say the back axle from a subcompact car. Out front, you use the rear half of a scooter, the kind that doesn't require a license to drive on the street. These things are good for 35 mph, unmodified. You have now got a 3-wheeled motor scooter, with the paperwork from the original scooter, street legal.
Sure, you could use a larger scooter or even a big motorcycle, but the scooter has no gear-shifting requirement to complicate it. Don't let that slow you down, I'm sure the linkages could be worked out. Law Dog might even appreciate this as a good exercise in recycling an otherwise undriveable police motorcycle.
If you're feeling artsy, you could even cover the scooter half up front with a shell resembling a horse. A small horse. Or a big dog. Or something. The mind boggles, no?