I too have had the onerous task of handling/oversigning imprests when I was in and it seems to me it now HAS to change.
The current system is from the dinasaur age. Aircrews of all brevets earnt them because of hard/expensive/professional training and because some one has certified that they are entrusted with other peoples safety. So trust them with their own Amex card account and let them settle their bills individually and leave the co-pilot to do his proper job. If some one screws up it doesn't then focus on the Co.
My advice to Flt Lt Oetzmann is sue the MOD after taking advice from his Solicitor. The Judge was damning of the MODs handling of the case just the like a Judge did earlier this year in my case. It will be a slow process and the MOD will try to grind you down but eventually they will pay up if you know you're in the right. I've receieved an interim but I'm not quite at full settlement yet.
One thing for sure is in his and my case the RAF departments who are supposed to be there to support the Frontline and its personnel have woefully let them down.
And they wonder why people leave?