I can second to waking up with the sun part and even more. I have been waking up like that for over 4 years now, started after I have realized my brain is capable of even waking up 3 minutes before my alarm rings, almost consistently. Without an alarm to rely on, it ticks even better, and even without the sun I can wake up the time I want.
I think everybody can do this, with just a little courage, and perhaps less caffeine. It doesn't hurt if you set an alarm to a time that is absolute latest you should be getting out of bed, requiring you to take a cab in a rush without shower or anything alike, and then even being 5 minutes late to your appointment. That assumes you commute via some slower/cheaper means. This is what I do when there is something really important and I never had to take a cab.
It is all about trust in yourself, and getting rid of kind assurances (grace alarms) and self-restrictions helps.