I wouldn't argue with any of those practical perspectives, but think differently for a second. In principle, would it be good to see a Lightning flying again, to see the Vulcan continuing to fly.. and more importantly, to have in place a process which is forced to address heritage and conservation in the most general sense? Think about the principle, and think ahead.
The current BBMF inventory will not remain flying for ever, and then what? What will the RAF have to remind the nation of the part it has played? Lets not forget either, that BBMF started out as the Historic Aircraft Flight, so proposing this is nothing new anyway (one for the purists!). If it means some kind of PFI, then so be it. Something this long term and important needn't automatically be entrusted to the MoD.