the USN/USMC would not be giving their newest types to minor Commonwealth air forces. Not a chance.
Except that was precisely what they had been doing for years. RNZAF was flying F4U-1D Corsairs with P-51Ds en route as the war ended and P-51Ms on order, RAAF was flying B-24s, B-25s and P-51Ds (100 P-51Ds shipped in 44, though most production was intended to come from CAC). FAA was flying F4U-1D Corsairs (and at sea before US) and had been due to get F4U-4s, although these were diverted to USN use, Hellcats all the way up to the F6F-5N, and TBM-3 Avengers, RAF and RCAF in Europe were flying P-51D/K Mustangs, in India the dominant RAF and RIAF fighter was the P-47D Thunderbolt, with US 2 and 4 engined bombers such as the B-25J getting a lot of use pretty much everywhere, even when RAF priorities pushed the 4-engined types into second-line roles as happened with a lot of Liberators and pretty much all Fortresses. France had P-47D Thunderbolts and F-6 Mustangs, Russia, Mexico and Brazil had P-47Ds, China did get a lot of second line aircraft, but also was flying P-51Ds and B-25Js, And all of these transfers happened while these aircraft were the then newest types in US service and while significant numbers of US units were using theoretically older machines such as P-40s.
I'm not saying that the allied units would have priorities over the US forces, but the evidence is pretty overwhelming that supply to allied units proceeded in parallel with US deployment, not following it and I haven't seen any evidence to say this wouldn't happen with late-war variants, in fact the Kiwi P-51Ms say it was happening.
OTOH, the UK had its own late-War aircraft coming into service and the need to supply the RAF with Lend-Lease types had dropped to an extent, with RAF types able to take the place of many US aircraft. The one exception is perhaps a long-range escort fighter to parallel the P-51M/P-47N, but the Hornet would have some potential there.