I like that. You could even weld a rounded "keel", or just cut a large steel pipe in half and weld it on the bottom of your chariot say 3" or so higher than the bottom of the wheels, so when, as FDH points out, it wants to sink in soft ground the "keel" will still allow it to skid its way out until you hit harder ground again.
In really soft stuff the keel probably would not help epsecially pulling with a ATV. But it might make a difference in alot of stuff that the narrow wheels will sink int. If it sinks all the way to the bottom of your chariot you are stuck. the keel might prevent that from hapenening. Just thiking off the top of the noggin.
Really cool design though. Lots of potential for when a big arch is not necessary.