Thing is, the reason they went for Malaya first was to neutralise the ability of Singapore to operate as a base. Malaya was attacked on the 8th, and the only other places even touched in December (apart from the Philippines) were Brunei and Kuching.An alternative, if they think the British in Malaya are now too strong for the forces available, is to scrub the Western arm of the operation completely - hit the Philippines fast and hard, neutralise the garrison there, then make Davao your forward base (as OTL) and push South through the Makassar Straight and the Banda Sea, aiming to take Ambon and Timor and the oilfields in Eastern Borneo, then roll up the East Indies from the East. If the British shift forces from Malaya to oppose you, they have to move away from their air/naval bases at Singapore and (probably) leave their heavy equipment behind.
Once you've taken Java and Sumatra and closed the Sunda and Malacca Straights, Malaya can no longer be supplied and (like Bataan/Corregidor) is effectively a self-supporting PoW camp. The trapped Commonwealth forces there can be eliminated with a combination of landings in the south and a land offensive down the Kra Isthmus, using troops freed up by the end of operations in the Philippines and the East Indies.
But I suspect it's more likely that the IJA will decide that a single additional brigade in Malaya doesn't change the situation enough for a major revision to the plans.
Also, good to hear about North Africa. Having to resupply over the beach will get them thinking about how to do that in future.