Mr Grim,
Yes a UAS can spend hours on station, and if you have a fairly static situation, that doesn't require your CAS assets to reposition rapidly, or to engage a number of widely geographically separated target sets then its low transit speed isn't an issue.
But looking how FJ air power is used in Afghanistan, that's quite a big 'IF'.
Moreover, looking at the average sortie lengths actually being flown by 39 Squadron, it's clear that the RAF's UASs are being used for missions that could be flown by manned platforms.
And yes, purchase price is low, though the infrastructure requirements and manning required by Predator/Reaper has been massive, and the aggregated cost per mission is high, because the loss rate is staggering.
And if you seriously think that a UAV "can do 90%+ of the current FJ AG role" then you're seriously deluded.
Small scale UAV ops are great to build up expertise in this area, ready for when it really does become a game-changer, to develop techniques, technologies, and tactics and to gain a fuller understanding of capabilities AND limitations.
But at the moment, we are using our UAVs largely for missions where:
a) Their 'loseability' is not an issue (the losses have not been due to enemy action, and a manned aircraft would not have been lost in the same circumstances).
b) Their extended endurance capability is not being exploited.
c) manned platforms would do the current job cheaper/quicker/better and above all with much greater flexibility.
I wonder whether ZA179, ZA180 and the others reflect a recognition of these limitations?