It would be neat if they could include the M1917, but I don’t really know what other pistols could be included that saw considerable use by the US. The M1911A1 is, well, that’s by far the biggie. Adopted 1911, used in WWI, improved from the M1911 to M1911A1 in 1924 or so (all changes were external, 7 I think, internals are the same, improved handling and possibly slightly improved reliability with the expanded ejection port), and that’s how it went until modern day where some US Forces to my knowledge still field a 1911 variant via the M45A1 or whatever it’s called. Maybe just M45.
It’d be neat to include an M1873 Colt Single Action Army, however, who on Earth carried one of those in WWII? If anyone did, they’d surely be a one-off like balls-of-steel Mad Jack Churchill with his longbow and longsword.

It probably didn’t see actual use in WWII but it confirms that at least one was present. I realize that films can’t always be trusted to be historically accurate, but the movie Fury about a US tank invading Germany in April 1945, they have a revolver in the tank. It’s not a Colt SAA, probably double-action and swing-out cylinder. .357 Magnum has been in production since 1935 it seems, according to Wiki, so that could be included. In the film, the team in the tank Fury had fought together in Africa, in France, I think Belgium may have possibly been mentioned, and of course it is set in Germany. The team had survived intact until shortly before the movie starts, where it’s soon revealed that they lost their ‘bow gunner’ as the tank commander puts it, I refer to the machine-gunner in the front as the ‘assistant gunner’ though it may be incorrect, I don’t know. They get a fresh recruit, not even someone trained for tanks but instead trained to be a typist, and so we witness this character being exposed to front-line action. Anyhow, my point is, they’ve been to so many places and been traveling for so long, also picking stuff up off of German corpses for so long, they gathered a nice collection of items, including an STG-44 which was probably a pain in the ass to pull out of or put back into to the tank.
Anyhow, yeah more pistols would be fun, though there’ll always be the argument that anything outside of the M1911A1 and M1917 revolver would be fairly unrealistic due to having seen little-to-no confirmed use by the US in WWII. So meh, I can’t really give any suggestions. Only having the M1911A1, though I love it, does leave the side-arm situation for the Normandy campaign pretty monotonous, but it’s THE pistol of America for WWI, WWII, Korea, and Vietnam. Right now, the sidearm selection of the US is realistic, and adding more would dilute realism, but why the Hell not? If we’re getting scoped M1 Garands and M2 Carbines and plenty of M3 “Grease Guns” in the hands of infantry, plus the Sherman Jumbo, on the beaches of Normandy… kinda opens the door for the suggestion of “If it existed during WWII at any point, even if it didn’t leave the prototype stage, have at it!” I mean, the freakin’ Pederson Device is in the game… stuff like that really sticks a thumb in the nose of anyone who tries to guide the game along the lines of realism.