Old Ned, your tone suggests you are a nice bloke, so in the midst of my rage I will try and give you a straight answer.
Having done a non-flying but flying related tour I would have been p!ssed off in the extreme if my pay had been cut for doing a ground tour that I didn't really want to do, but that someone had to. I was lucky (!) enough to get posted into the job because I had worked hard and had all the quals you could get in my branch. So, the poster needed the job done, I fitted the bill and (shush, don't tell anyone) but I realised I might be able to do some good. Now, if the poster had told me, 'well done BootFlap, you have been selected to fill this post that also means, and you'll like this, you take a pay cut.......' the GPTN line may have mysteriously cut off to the ethereal sound of a gently exploding pilot extolling the virtues of PMA desk officers getting 'down and dirty' with their own arses! (For the colour blind, that's telling them to go and f@@k themselves!) Therefore, if you want experienced aircrew in these posts (and from experience, the presence of a friendly aircrew mate can save time and effort on many peoples parts) you cannot penalise them. If you do, they simply will not come! Therefore, some poor engineer will be stitched with doing an aircrew job. Now you may initially think, 'fantastic, not a snag'. However, I would argue this is akin to having an aircrew mate do the Eng Ops or Line Controller job, after all it is not actually engineering, is it? Or maybe, just maybe, the experience gained through training and hard work, in all trades/branches, means that all have something to offer, and the combined efforts make for a better result.
Now then, Flying Pay! Sorry, but this is market forces in its purest form. A short search on t'internet will give rough salary scales for any job out there. If you were brash enough to equate OC Supply to an Argos Store Manager (I know, i know, Argos actually delivers!) it will give you a rough idea of an equivalent wage outside. I will not give any more examples, because only you know your true worth (mine's 2 Magners and a knee trembler behind a 197x Viva E Coupe, but that's a different story!), but trust me the airlines and BAE are paying well. I don't want to leave, but after 21 years of near continual Ops my family wants cash! I will be sad if I do leave (still undecided) but I will not be bitter; I only wish others would accept the Force for what it is, and more importantly, what it should be, just a 'chuffing big Sqn'. Look after each other, accept we are different, get down the pub when able, tell jokes about non-PC birds with bad arthritis and get on with it.
Rant over, if I offend, I apologise. It's been a bad night.