Guys, I found a phd dissertation on the development of the Greek Armed Forces in Egypt in 1941-1944. Unfortunately it is in
greek, but it has a lot of useful information that can show how the exiled greek forces can help the Allied effort.
In OTL, the ships that escaped to Egypt were 1 armoured cruiser, 6 destroyers, 3 torpedo boats, 5 submarines, 1 repair ship and 3 transports. At January 1st 1942 the Greek Navy-in-exile had 241 officers and 3,643 NCOs and sailors. By the end of the year it had 340 officers and 5,785 NCOs and sailors. If the full 18,000 men of the Greek Navy are evacuated, then the Allies gain a lot of trained naval personel. Moreover, many more transports could have been saved, further increasing the available tonnage in the Mediterranean.
In Egypt a battalion has been already formed by local Greeks. By this time, the Evros Brigade of 3 infantry battalions has been interned in Turkey and will find its way to Egypt as in OTL. These 4 battalions formed the manpower for the 1st Greek Brigade. By November 1941 a 5th infantry battalion was formed from escapees from Greece (there were basically no greek escapees from the Battle of Crete). By early 1942, 3,912 men from the greek diaspora in Egypt, Palestine and Sudan had joined the greek forces. By February 1943 the Greek Army had around 11,000 men in two brigades.
Now in TTL, there are 3 additional sources of manpower: the formations saved from the front, the 50,000 green recruits, the ~11,000 National Guard volunteers from Crete (capable only to act as garrison troops in Crete) and some other units lost in OTL in Crete (e.g. the Cadet School). From what I have read in the timeline so far 8 infantry divisions (I,II, III, V, XI, XII, XIII, XX), 1 Cavalry Division and 1 Infantry Brigade (21st attached to the Cavalry) may be saved. Certainly there will be a discrepancy in the manpower of each formation. The XII and XX divisions will be sorry remnants. The V division will be the strongest since it had received additional reservists in early spring and at April 20th it had just over 20,000 men (some Cretans from other units flocked at it during the retreat). The rest of the divisions will have a reduced power of 10-20% if we judge by the OTL experience. If the XII and XX are disbanded to fill up the rest of the divisions, there can be 6 Infantry Divisions and the Cavalry/21st Brigade (waiting for tanks and training to be turned into an armoured division). If the V "Cretan" Division with its 20k men and the Cretan National Guard (11k men) form the garrison of Crere after the initial battle (if it takes place at all), it leaves the equivalent of a small field army for the Allies to play with. This field army will have access to at least 61k men as replacements. I say at least, because with Crete in Allied hands, there will be a greater tickle of men and officers escaping the brutal occupation of the mainland.
Where am I getting at? Certainly it will be some time until all these greek troops are re-organized and trained to mechanized warfare. In any case they will be very useful in the years to come. However, in the short-term, a portion of these troops can be utilized as garrison troops in Egypt, Palestine, Syria and Lebanon. The OTL garrisons could be freed to used in other theaters. If e.g. British and Commonwealth policy makers want to send an additional infantry division in Malaya at October 1941, they will have the ability to do so. If you have to house and retrain so many pesky Greeks in Palestine - most of them veterans, surely there is no need for the 1st Cavalry Division staying there in order to transition to the 10th Armoured. There may be an imperial backwater to send the division to be formed and reassure the Australians.
After all, there is finite infrastructure in the Levant that cannot support both the Greek Army and that many Commonwealth forces. It makes perfect sense to me, that saving a portion of the Greek Army in April 1941 can result to an additional corps in Malaya in November 1941. Talking about butterflies, huh ?