What if Metaxas lives through the beginning of 1942 instead? Does it change Greek strategy or any outcomes, at least in the short-term?
Not that I see.
What if the Italians invaded Crete and or the Ionians at the beginning of the war or within a week or two of its start? Per the ever--reliable wikipedia analysis, "Another notable failure of the Italian offense is the lack of any attack on the Ionian Islands or Crete, which were obvious and relatively undefended targets and could have provided Italy with strong forward naval and air bases."
Corfu, maybe. But for what the air and sea parts of the campaign mattered,
that's not all that useful. Crete, no. There isn't the strategic capability
to support such a long-ranging operation. The Greeks would have little to
oppose the first-day operations, but then it would just be up to the
weather, distances, shortage of logistical lift, and British submarines.
What would a good Italian plan to invade Greece in autumn 1940 have looked like?
Well, not starting with that few troops in Albania to start with; but having
a sufficient number of troops means substantially boosting Albania as a
logistical platform. Building up port handling capacity, military bases, and
above all roads. You just can't do it with the Italian annexation of Albania
on its actual date.
A landing not on Corfu but on the mainland Ionian coast, say at Igoumenitsa,
would have been a good idea; but not a quick war-winner, considering, once
again logistical constraints (small port, bad road leaving it etc.). It
would have given the Greeks more of a headache.
Naturally to do that, you probably also have to land on Corfu.
Such naval operations require, of course, time to prepare, which the
Italians lacked in OTL.
Could the Greeks and British have seized Rhodes and the Dodecanese
from the Italians between October 1940 and May 1941?
No. The British however are likely to bomb it at will one day or another,
making a propaganda point mostly.
What's the hardest possible time the Axis could have in Greece, with
any PoD after October 1940?
The Germans don't intervene and the Italians remain stalemated and
humiliated more or less where they were at the end of their largely
unsuccessful March 1941 counteroffensive. For this to happen, Yugoslavia has to be German-friendly. The British might also not intervene save in sending the Greeks war materiel. That has a kncok-on in North Africa, with the Italians probably pushed back all the way to Tripolitania. I don't think
that even in this case Tripoli falls, but Tripolitania remains the only
African bridgehead in Italian hands by the end of 1941.
What if the Italians decided one war, the one against the British, was already too much, and refrained from Balkan aggression?
Well, good idea. However, it's not really as good as it might seem because of the usual very well known problem: forward ports in North Africa had roughly the same insufficient handling capability as the Albanian ones. So it's not as if all the divisions that were used in Greece can all of a sudden be shifted to North Africa and make a difference at to preventing the Compass debacle.
Some of them, however, can reinforce Tripolitania, thus confirming the outcome I mentioned above; the British advance a lot into Libya but don't wipe out the Italians from it.