the burden should be on the state to prove beyond a reasonable

It absolutely should be, but in lieu of mind reading technologies we need to set some boundaries that establish what we mean with intent to drive.

I can't just be walking down the street holding a pound of cocaine "for a friend", I can be arrested for intent to distribute even though you haven't gone through my mind to understand what my true intent was. There is a (arguably arbitrary) boundary that establishes intent.

Similarly for motor vehicles, that boundary must be established. With a car running, sitting in the drivers seat, assuming hand/feet on or close to the controls, we establish intent in the law. The law would like to stop the crime as early as possible to avoid other injury.

Could the friend not have gone back into the bar and waited there?