Those are both interesting, but as "home" units, approaching an irregular status. The Chinese Nationalists used the Hanyang 88 as a standard issue individual weapon in WW II.
Anything come to mind predating those?
Soviet's using Berdan's?
There were small numbers pulled out to use during the "Oh shit we have no rifles" days.
Otherwise the Greeks and the Gras would be the oldest I can think of.
As for the topic at hand, ignoring the logistics issues (which already is a big ask, but not impossible as some think) I think trying to do this really would be strangled by cost issue. The British simply can't afford them, and before you say they would be given under lend-lease, I have to ask, why would Britain accept them?
The other lend-lease equipment they took to fit shortfalls in what was available (Shermans, supplies etc) within British industrial ability, but the M1 Carbine doesn't do that, so all it would do is place another, unnecessary, weight on the back of the camel that was going to be British post-war finances. I mean it would serve the US great if it happened (faster decline of the British Empire being one of those oh so happy side-effects of Lend-Lease) but not the British.