I'd agree with everything but the last point. Crete makes a terrible place to base heavy bombers. First of all, you need to construct the bases. This requires huge amounts of concrete, which has to be shipped in. Next you need the fuel, ammunition and sundry other supplies, which need to be shipped in. You then need to store all these things, which means tank farms, ammo bunkers etc, which requires more concrete. Sustaining these ops will require huge volumes of supplies, so you'll need to upgrade the islands transport net to cope. This means oil pipelines, better roads, possibly small railways with attendant marshalling yards. This requires more concrete, steel, and other supplies, which need to be shipped in.
Problem is that the decent ports are all on the north side of the island, making it riskier sending in all this shipping. Yer probably too small to cope with sustained ops, so you'll need to upgrade them. More concrete, steel, etc. Now don't forget that heavy bombers are EXPENSIVE, as is all the infrastructure you have to develop to support them. Can't have the Germans staging a paratrooper raid and knocking out your airbases. Yes we know that it is unlikely, and the British may believe this due to Ultra, but how much risk do you want to take? So along comes some additional garrison troops, heavy and light AA, fighters, night fighters, radar etc. All of which require even more supplies. Crete is still likely to be an outpost though, much in the same way Malta was, with little opportunity to develop a layered air defence environment. You are likely to have contest air space at best, and the attritional nature of this will place further demands on your logistics. Meanwhile, if one raid gets through and knocks out 30-40 bombers on the ground, you lose the £ equivalent of a battleship. Not really worth risking it, especially as the bases that you are building are on Greek territory, so aren't likely to be strategic assets after the war.
Better to bombers somewhere more logistically feasible, with better existing infrastructure, better defensive options, and less risk that he colossal investment in blood and treasure will end up outside of London's control/influence post war.