I'm a big fan of Streisand and her version of "A Star Is Born". I thought Kris Kristofferson did an excellent job in the role of John Norman Howard. I think Elvis could have played the role, however I think it would've been a very different movie.
I can't imagine Elvis doing drugs in a movie, or allowing himself to portray an artist in decline. (Even though he was really playing the part in real-life.) I think his version of the role would've been very different.
The soundtrack of the movie would've been different as well. Paul Williams wrote a lot of the score. He's an excellent writer, and I would be really interested to hear what he might have come up with for Elvis. Elvis had a lot better pipes than Kristofferson!
Streisand had a lot of control over that movie and the score, I just wonder how that would've worked with the Colonel and his business dealings and what not. What about Elvis' billing and his standard part of the publishing and profit, etc? There almost would've surely been a clash between the two camps.
Fascinating to think of nonetheless.