Parsifal, would area bombing of cities been the best use of Mosquitos? Considering that they could potentially hit targets more accurately bombing from low level and/or during the day?
Perhaps the RAF didn't need more Mosquito light bombers. What they needed were more accurate bomb sights for existing Lancaster Bombers plus a long range fighter aircraft to protect the bombers.
There is another possibility too, that the Mossies could be used as diversionary targets, to split the LW N fighter defences.
If you had several groups of Mossies flying out to different cities at the same time as the main (Lanc) raid it forces the LW to try to intercept multiple raids, as they can't tell which is the primary, so your heavy bombers are only facing a fraction of the NF.
Another tactic that was suggested was to have small groups of Mossies raid multiple targets strictly for nuisance value, it was suggested (by the Air Ministry) that a dozen or so Mossies caused a large disruption for little chance of loss.
Even a small raid would result in 10's of thousands of people woken up and sent to air raid shelters, NF scrambled, AA personnel mustered and ammunition wasted.
I've read that it takes at least 5,000 - 10,000 AA shells to bring down a bomber, so the Axis are using up resources to make guns ammo that won't be used on the Eastern front. Meanwhile, the Mossie flying at a much higher altitude has a lower vulnerabilty to the flak.