AAR for the Nimrod is a force multiplier, not a force enabler (for example, as it was for the Muharraq Tornados in Gulf War 1 tasked on long range attack sorties).
If Nimrod AAR is as dangerous as it certainly now appears, then you will need more Nimrods to cover the same period as a single AAR-supported aircraft.
Which means a lot more money thrown at fixing and upgrading the Nimrod fleet to the 'special' fit needed in Afghanistan.
Suck it in and cough up, Fat Gordon!