As one who has no experience with modding this game (though quite a bit in others) my question would be how hard it would be to make this an optional mod.
Greyrider's correct - I don't know what WWII US Navy binos were like first-hand, but the Canadian Army binos circa late 80's early 90's were precisely as he describes them - which should tell you something about Canadian Army equipment pre-war.

(Heck; when I joined in '86 we still used bloody Sten guns!)
Is making this change simply a matter of changing the optical image and adjusting the magnification? If so this is an optional mod I'd personally love to see.
EDIT: You know what? I love making adjustments and this one looks like one I can try. I'm starting to get used to the file structure of SH4 and this might be a decent project to attempt if Greyrider doesn't mind; as a learning project if nothing else.