There was once a time when I was part of a team assessing tenders for "commercial" turbofan engines to be used in a British large military aircraft upgrade programme. Any similarity to projects discussed above are purely coincidental. My particular area on that programme was the through-life support aspects. Each of the tenderers were offering tweaked versions of the "guaranteed availability" support contracts which they had with their commercial customers. Under these contracts if an engine fault or failure caused a mission delay or cancellation the engine supplier would pay a financial penalty - quite a large one. This was an off-the-shelf engine with an off-the-shelf support package. But I had to explain that being paid money wouldn't fix it - the military mission was different. That was the event which I crystalised in a section of a dissertation I did many years later (which I'll post seperately) Two of the suppliers actually grasped the point, but each then said they would need an initial £5m(ish) for non-recurring engineering to explore and scope the development of a bespoke support package. They also pointed out that the *standard* support package was contingent on achieving the specified utilisation rates - bounded at between 25% and 60% of elapsed time. These are typical in the commercial world, but the military mission amounted to a few hundreds of hours per aircraft per year.
That's the problem with off-the-shelf procurements - they're developed to match SOMEONE ELSE'S requirement, and if your's is different it will cost you.
PDR