Force Z survives Dec 10th 1941 and is then maintained as a ‘fleet in being’ (Churchills desire apparently was for POW and Repulse to become a threat to Japanese Ambitions like Tirpitz had become to the British)
There are several PODs that should allow Force Z to escape serious damage on the 10th Dec 1941
1) More disruption to the attacking air groups. While the various Strike groups attacked in a disrupted fashion anyway (they had split up to find the fleet) – Early in the battle 1 group of bombers had attacked a destroyer, HMS Tenados (which was operating alone ahead of the main force) having wrongly identified it as a battleship and dropped their ordnance on the WW1 Destroyer for no effect.
It’s possible that this attacking wave of bombers could have directed more of the attacking waves onto this wrong target and this would have resulted in less planes attacking POW and Repulse.
2) More ships. Several Light Cruisers were at Singapore.
HMS Durban, Danae, Dragon and Mauritius. Now the first 3 are older ships but HMS Mauritius, a Crown Colony Class is Brand new with a comprehensive and modern AAA Suite.
Apparently there was a design fault where she was equipped with a self deguazing system which had caused serious corrosion to her fire main and attempts were underway to repair this in Singapore.
Seems very un Royal Navy to me for a ‘first rate’ Ship like Mauritius to sit out a potential battle and its not too much to imagine that her crew manage to get her ready for battle in time to sortie.
If Mauritius and a number of the other Cruisers had accompanied the fleet the additional AAA / potential targets might have made a difference.
3) This is the most obvious one. 453 Squadron RAAF through foul means or fair manage to maintain a partial or even full cover over Force Z. The units acting commander believed that he could have maintained a rolling cover of at least 6 fighters throughout the day and had even come up with a plan but received a negative response from Adm Phillips and his staff. Apparently the Commander of 488 Squadron RNZAF also proposed the same thing but again his plan was turned down.
We know from other engagements that even the prescience of a handful of fighter planes can seriously disrupt an attacking formation. Certainly there would be less chance of the formations turning up and attacking anywhere near as effectively as they wished and managed OTL if there was friend fighter cover.
4) Perhaps even more obvious. In the absence of proper intel and decent air support – the fleet stays in port. This for me in hindsight is probably the most obvious POD but several things mitigate against it. Firstly – so un Royal Navy it verges on ASB for them to sit in port while their enemy sails where he pleases where their exists the potential to stop him. Particularly when the RN knew that the Army and RAF was being hard pressed to the north. Secondly – they had seriously underestimated their enemy - he was, so they thought, Buck Toothed and short sighted and flew Obsolete biplanes that could hardly fly let alone threaten capital ships. So I dismiss this as a realistic option.
So a combination of the first 3 results in a stronger and better defended force Z that is more able to survive its encounter with the various IJN Land based air groups.
Then once returned to Singapore the Force becomes the core of a ‘Fleet in Being’ with 2 Capital ships, 4 light and 1 heavy Cruisers and a gaggle of Destroyers – what effect could/would this have had on subsequent events particularly if later reinforced with ABDA ships (which alone struggled to have any impact) and later in March 1942 by HMS Warspite, the 4 Rs (if all 4 were sent) and a fleet carrier or 3 (not necessarily British)?