I agree that the existing .45s in military inventories have a lot of wear and tear. A friend of mine bought a Remington 1911 .45 with a mfg. date of 1944, built for the war effort, and it's a beast.
At the same time, I just bought a new Para-Ord P14, specifically because the double-stack magazine made for a thicker grip. In field testing the Para vs. several single-stack guns such as Springfield Armory, Kimber, Charles Daly and Les Baer, I was consistently more accurate with the Para and the gun felt much more comfortable in my hand (no surprise).
It will be interesting to see who gets the contract if the U.S. military switches back to the 1911. I don't know that the double-stack configuration would prove to be that much of a problem for soldiers and marines who were properly trained in its use.
And of course, the extra capacity -- 15 rounds for law enforcement and military -- would be an extra bonus in a firefight.