Its sane. (I'm planning something similar, but a bit shorter, so I have to say that) Go for it.
Overall average of 15kmh.
The conclusion that I've come to (and I'd be happy to be corrected) is that it would probably be best to start in the morning after a full night's sleep. This means you'll finish in the morning and your 24hr period will not be "a day". While this may take the edge off the challenge headline, it means you're minimising your sleep deprivation.
Vehicle support would mean you can keep weight to a minimum. Sounds like an adventure.