I carry a Para-ordanance P-12 compact 1911 variant in .45cal.....
Have for almost 20 years....
Extra rounds, lightweight amd extremely reliable plus accurate.....
Too short a barrel for Military carry but there are pleanty of good high capacity 1911 variants.....
The larger issue is why are they focused on 9mm and not other rounds?
See the exhaustive FBI handgun study that was released a couple of years ago. It was the conclusions of this study that convinced the FBI to go back to the 9mm. There is an excellent two part summary of the study on youtube that you should be able to find with a search on the youtube search engine. (that's how I found it). It is very enlightening. The basic crux is that the concept of greater "stopping power" of a .40 cal or a .45 cal is a myth. The key for a handgun (which is an intrinsically defensive weapon) is being able to fire accurate, fast follow up shots and all of the FBI shooters from the best to the merely adequate were able to place quicker, more accurate follow up shots with the 9mm.
“The larger issue is why are they focused on 9mm and not other rounds?”
It is cheaper and lighter. Less material goes into the round so it will always cost less to make. Less material also means for the same weight, you get more rounds. Same reason the soldier not carries a .22 caliber rifle rather than a .30.