Canada pretty much did exactly that, 2 pounder guns on a 6 pounder carriage. I think it was due to production of the guns not keeping up with the production of the mounting. Australia trialed an airborne 2 pounder, sort of a 2pdr tank mount stuck in a 6 pounder inspired split trail, but it wasn't really any better than the usual 2pdr carriage and the 2 pounder itself was on the way out so it never went anywhere.
I wouldn't be surprised if there was one or more British simplified carriages lurking in archives somewhere too.
