As it mentioned, the ships en route to Alexandria can be used either against Rhodes or Tripolitania. What would either target mean?
A landing in Rhodes has a meaning only as an island-hopping campaign at the Aegean. The ultimate target would be to establish fighter bases in strategic islands at the north (Lemnos in particular) to assist the future bombing campaign against Ploesti. At the same time, the Dardanelles would be closed to Axis shipping. Romanian oil cannot be sent via sea to Italy. Last but not least, it increases the threat of landings over a vast coastline spanning from Thrace (Alexandroupolis port) to the Peloponnese. Otherwise, Axis-held Aegean islands act as a security barrier. So an island hopping campaign would tie down a significant number of Axis divisions on the coast of mainland Greece.
However, if an island hopping campaign is not in the plands, Rhodes on itself as little value. Crete itself would be a better-suited unsinkable carrier. In that case, Libya would be a more desirable target. Due to the distances involved, the alt-Crusader with Sirte as a starting point would limit the number of formations that can take part. Of course the same applies to the Axis as well, since they have left only a single port and the RN can safely-ish operate in Central Mediterranean with Crete and Cyrenaica in Allied control. So, both armies will be weaker compared to OTL Crusader, the Axis
considerably more with very little armour. It would made certain sense to land a brigade group with armour behind the Axis frontline to ensure the Italians' complete destruction (few Germans would have been left by that point in the Axis OOB).
Overall, both the Rhodes and Tripolitania choices have their merits. What is certain though, is that the Allies have more divisions in the theatre than they can supply in Tripolitania while Vichy Syria is much less threatening compared to OTL. I think the author has dropped a hint about which formations will be sent to Malaya.
The question that is rising is whether the two brigades and HQ will stay in Malaya or if they will be sent to Ambon, Timor and Rabaul.
Lastly, I want to ask
@allanpcameron what is the status of the formation of the Australian Armoured Division or at least its first armoured brigade.