I wonder if any of the forces used in East Africa will now/soon be redeployed to the Far East? Even a small amount of men with combat experience and knowleadge of tanks could make a big difference in Malaya. As would even a small amount if modern equipment above OTL levels.
North africa and Greece are far more important right now for any troops to be sent to the Far east. We are still roughly 6 months away form the Japanese being seen as a threat.
More good troops in Malaya means more good troops captured by the Japanese. The army forces in Malaya Command weren't great but they were perfectly adequate to stop the Japanese 15th Army providing
a.) The RAF presence is of sufficient scale and quality that the Japanese don't acquire total air superiority
b.) The RN presence is of sufficient scale and quality that the Japanese don't acquire total naval superiority
General Percival was awful but he had a very difficult job because any defensive line he formed could be outflanked by a naval landing and as in France in 1940 air superiority is a massive force multiplier.
Now an earlier end to the North Africa campaign i.e. pre October so there is enough time to get RAF and RN reinforcements to Malaya would be a complete game changer. But I'm not sure Britain can reach the Algerian border. While in OTL the advance to Tripoli post El Alamein was incredibly fast that was because Montgomery had amassed an enormous stockpile of engineer stores so he could repair the coast road and railway line very rapidly. Here none of that has been prepared.
More troops is enough assuming they are properly led even with the air force deficit, it is difficult though. The main thing more troops gets you is more time to redeploy the assets you need to actually stop the Japanese.
As for reaching Algeria, that is completely possible within the next six months. A big part of the reason the British have stopped is to build up the forces needed to push on to Tripoli. Once Tripoli is within artillery range even then the game is effectively over unless the Axis go into Tunisia and that might make things worse for the Axis not the British.
i think this is the 10th time i mention this here but you cant save singapore with this minor of a pod altough butterflys are finally starting to flap their wings i think finally but not enough without hindsight helping things along. You could do alot better in the fight and delay the fall a few months even but thats it i think . Instead i propose a more extensive burma campaign especially in 42 when the brits arent distracted yet and are building landing ship stuff and do a practice run or two at rhodes and other islands in the eastern med . If burma campaign goes well enough you could liberate singapore yourself wich would help british prestige wise .
Saving Malaya is completely possible given the POD. A small change over time can lead to big changes and we are 6 years on from the POD ITTL. The advantages the Japanese had are easy to overcome with even a couple of small changes.
The lack of experience of the Commonwealth forces is easily remedied if experienced troops are able to be redeployed from North Africa ITTL.
Experienced troops will not only point out that armour is perfectly viable in Malaya but will also be able to withstand the Japanese armour far more effectively even if only poorly or completely unsupported.
The ability to redeploy troops means that Air resources can also be redeployed so that advantages is negated somewhat or possibly completely.
The same is also true with Naval Assets and any additional naval assets, especially carriers will make further Naval operations very difficult if not impossible.
Finally more troops being able to be sent means that the numbers advantage the Japanese had will likely not exist, that not only helps in head to head fights but means that some of the units that were isolated may well not be making things better again for the British.
All of that is eminently possible ITTL. It is also important to remember that the second line British Equipment ITTL like the Matilda II and A15 are more than capable of taking on the Japanese equivalents as are the lighter elements.