SF CIF companies went to Glocks, both 9mm and 40 S&W, quite a while back. They can access Army inventory 9mm for training and carry the 40's for combat.
As you stated, the gun NEEDS to be a double stack. A Glock 21 is too big for many.
Going back to a 1911 would be like going back to Cocoran Jump Boots and cotton shelter-halves. They both sucked way back when, and they would suck even harder today. The Quantico-built 1911's the MARSOC guys had broke constantly. Their new guns cost over two-grand each, and the one MARSOC guy I talked to recently said he'd swap it for a Glock in a heartbeat.
THE answer, IMO, is a Glock 37 in 45 GAP. That by-passes the large frame issue (G19/17 frame size), has adequate capacity (ten rounds) is cheap, and most importantly, won't break. The Army doesn't have much 45acp ammo left, or 9mm for that matter. Current ammo stores could be quickly depleted by current service guns as the new guns/ammo were brought on line.
