agree there is core role for civvi engineering support. It is clearly cheaper but there is a risk, as you say, of the experience and best practice migrating to the civilian end as that is their sole focus.
What is being discussed is Maintenance Policies. Personally, I think MoD has gone too far away from the traditional Line/Depth model. Today, I understand, what was 2nd/3rd/4th Line, and Depths B/C/D, is mostly contracted out. This results in a loss of flexibility and produces maintainers who are good at swapping LRUs and pressing “BIT” buttons.
The other side of the coin was demonstrated to me very early by one example. We (HQ staff responsible for availability, maintainability, reliability) always monitored proposed workshop postings. I was given the heads up that a Chief on Portland’s radar bench was to be posted elsewhere. We had no say in this - later, in MoD(PE), we could intervene, but not as part of the RN. His relief was completely untrained. The increased arisings at 4th Line cost an extra £1M per year, because the Recovery Rate at 2nd Line, required to be 80%, plummeted to mid-20s. (All support funding is predicated on these Line Recovery Rates). That money had to come from somewhere. And that’s just one piece of avionic kit. That was mid-80s, and one suggestion - swiftly shot down - was to have civilians (MoD or contractors) and servicemen both working on the bench at 2nd Line (ashore), the former providing the continuity to maintain the Recovery Rate. In the case I describe, the sensible solution was to send a Fleetlands diag on 6 months detached duty to Portland, at minimal cost (or at least slightly less than £1M subsistence allowance), but this was shot down as well as it would be to admit a problem.
I concede it is a vexed subject with many possible “solutions”. But I’d say the current situation is driven by the perceived need for savings, without looking at efficiency and operational effectiveness. But I doubt if an accurate investment appraisal has been done to demonstrate actual savings.