Portraits from Photographs - to do? or not to do? That is my question.

I watched a great documentary about the early years of Elvis Presley's career on NH Public TV a couple of nights ago. I'm from the wrong generation to have been starry eyed about Elvis (I was in the 4th grade when the Beatles hit the US, and John Lennon was the one I liked. Actually, I fantasized that the Beatles would be strolling through my neighborhood of Norwood in Warwick, RI, and hear me practicing the piano down in my basement and come pounding on the door to inquire who was making such terrific music. They would beg me to tour with them, and I would pack my bags right then and there. Piano was never my instrument - I think that I would have been better suited to play a fiddle, or something with a bow - and practicing even for just 30 minutes a day was sometimes pure torture. You can see the purpose of my fantasizing...)
Anyhow, Elvis was a little before my time. Funny, he was playing in Providence the day I got married (June 26, 1976), practically next door to the church. That's probably the closest I've ever been to him physically. So I've never given him much thought. Elvis's songs that were popular when I was a teen in the 70's always seemed so cheesy. In the Ghetto is about the only one I can remember, and by then of course he had turned bloated and sequinned. He seemed plain creepy.
In the documentary the other night there were many photographs of Elvis as a very young man - when he was 20 - 21. This was before he'd dyed his hair black (to look more like his idol, Tony Curtis!) before Hollywood, and before he became the cheeseburger addicted icon. I was struck mostly by the vulnerability and the feminine beauty in his face. I really wanted to get out my pastels and draw him. (I had this same impulse watching the great Bob Dylan documentary, seeing him as a young man, too. There is also a feminine quality in his young visage. Is this what the young girls [and some guys!] go crazy for? This almost 50/50 blend of male/female in the features? It's very interesting. I fell for that too, when I was a teen. My first love was very androgenous and quite beautiful).
My point in all this rambling is, I wonder if I could ever make a decent portrait from a photograph? When I make portraits, it is key that people sit for me. I need to see them move, and see how they hold themselves, and see what their face looks like when they speak, etc, etc. I can usually tell when someone works from a photo - the grimacing smile is always a tip off. But then there are artists like Chuck Close and Elizabeth Peyton. Francis Bacon worked from photographs. I suppose I can only try it and see what happens. Elvis has triggered this urge - is painting on velvet next?