Unless you think you'd never resynchronize after moving across the world, it's pretty obvious that your wake and sleep time would have to be a lot more malleable than you suggest.
I used to travel from London to the Bay Area for work with some regulatity. The first few days were amazing, because the combination of westwards jet lag plus night owl meant that I was getting to the office nice and early every day. As the jet lag went away, and I started to acclimate to the timezone, it usually took me less than a week to be back to a night owl routine, even without the usual stimuli.
And it takes all those tricks for me just to maintain a 24 hour sleep cycle. What I'd like to be able to do is what I did in college and shift my sleep schedule forward an hour or two every day. Instead I have a sleep mask, I start prepping for bed at least an hour early, I take melatonin, I make sure not to eat at night, and I lie down in bed with the sleep mask on for at least 20-30 minutes and listen to programs that help me to relax. Then it takes me 20-30 minutes after I really decide to go to sleep in order to go to sleep.
And right before bedtime is when I'm most alert. Even if I stay up all night, at about 9:30pm I won't be able to sleep.
What is really bad is when I'm seriously sleep depped and I get to sleep at say 7:30 or so, and I can easily wake up after 2-3 hours and then be stuck awake until >3am in the morning.
So I use every single trick in the book and then can just barely manage to stick to what the rest of society thinks is normal and its a constant fight.
> Unless you think you'd never resynchronize after moving across the world
The synchronization is to the sun and its light, not to human clocks. That it seems to be the same is because the latter mimic the former, not the other way around. So you can't just use an arbitrary clock, not with any reasonable effort.