If you want to level the playing field, then first and foremost you'll have to mandate people's Copious Free Time. Then probably their budget.
There have to be some arbitrary rules, of course. Support vehicles may not be in the spirit of audax - whatever that's supposed to be - but you could say the same about all sorts of things that are permitted (eg. sleeping facilities and bag drops). If the vehicles aren't causing a problem to riders or controllers, then what's the issue?
I admit I don't really understand how someone doing something differently detracts from your own ride. Ultimately, it's a test of being able to ride a long way on a bike, not of secondary suffering. (See discussion passim on the year record threads.)