Getting away from the point slightly, if one wanted a 1911 in 9mm, the most efficient way to go about it would be to buy a Browning HP. No, it's not a 1911, but it is another classic Browning design in single action, is doublestack (which takes advantage of the 9mm's capacity) without being bulky, and shoots like a dream. I've never understood the 9mm 1911, unless one is looking for a smaller gun on the 1911 action or one wants a full-size 1911 in 9mm "just because" (which is always a good reason).
However, if one was looking for a 1911 in .38 Super and wanted a 9mm conversion for economic reasons (cheaper training), I say have at it. That's a dandy idea...just don't forget to keep up your practice with .38 Super as well.