Based on the firearms you've rattled off, it seems as though you're aiming for representative pieces from all the major powers. If that is in fact your goal, it may be fun to go after the sidearms of each nation you have the full length rifle for. So you could accompany your M1 Rifle with a M1911A1, your Lee Enfields with an Inglis Hi Power, your K98 with a P38/German Hi Power and your Mosin with a Tokarev TT-33.
If you've got your heart set on an M1 Carbine, by all means make it happen but most serious collectors shy away from reproduction parts so I'd suggest a standard M1 over the M1A1 paratrooper variation. You can always upgrade down the line should you find an example with the folding stock, but let me warn you, they are not cheap.
Here are a some images of mine. I know of a couple others tucked away in the private collections of some lucky guys here on CGN but I really doubt there are more than a handful of these in the country.
Anyways, best of luck with the collection! Be sure to give us periodic updates when you add new pieces!
- Chris