The problem in KJF is that you have to make tradeoffs - you can invest into keeping Africa, establishing a UK/US mainland presence in Asia or keeping the UK Pac fleet intact, but it always comes at a cost in another theater. I think that you either need to put extra pressure on Japan (by building an India factory or an agressive fleet placement) or contest Africa for a pre-planned KJF to work. With that in mind, unifying the fleet has two advantages:
it can enable a US2 move to Sol
it forces Germany to be careful around Africa, because UK can land with 3-4 inf plus air in Ken or Egypt. With that in mind, building a SAf factory on UK2 becomes a possibility (you send the loaded trn with Aus inf to SAf on UK2, and move the rest of the fleet to NSW) and you can kill the German Med fleet on UK2
That said, Japan can still send its entire fleet so Sol on J2 to thwart the unification and even if it doesn’t, getting to Sol and capturing and keeping EI are two different things. Furthermore, you have given Japan a good start on the mainland (and the income base that comes with it).