Longer,
To add to Tuc's excellent point - there are often many good reasons for modifying a commercial design. Quite often, they are required to operate the design under military rules on the Military Aircraft Register.
Of course, that raises the point of why put ATC gliders on the Military Register at all. It was certainly a help when a previous CAS wanted to 'big up' RAF strength by including them as 'deployable aircraft'.
However, there should have been no problem whatsoever in bringing these aircraft on to the RAF's books. Any competent civil design authority would have already had a solid safety statement, plus the required certification evidence to allow the PT buying the kit to asses the extent of compliance with Def Stan 00-970 and to request the required modifications. Once these had been cleared by the DA, they would have formed part of the 'as contracted' configuration.
Once the aircraft were brought 'Under Ministry Control', the PT would have, as matter of normal course, been required to demonstrate compliance with the required regulations to the relevant MoD Committees and Boards. Part of this would have been the required PDS contracts and the mandated airworthiness reviews. The 'as contracted' configuration and its associated updated safety statement would have been the baseline for the RTS.
I stress again - all this would have been an utterly standard, well understood and quite easy process to do properly. Unfortunately, as Tuc and others have so well shown, RAF senior officers spent a good bit of the 1990s dismantling the experience base as well as the checks and balances that kept the show on the rails.
I agree that there have definitely been some fairly scummy politics around closure of many VGS sites. but the central issue (for me at least) is the RAF's failure to properly manage the airworthiness of their fleet of gliders. Why? Because there is absolutely nothing to stop this sort of c**p happening to other aircraft. In fact, I know that it is happening to other RAF aircraft right now.
That's a problem. A big one.
Best Regards as ever to all those good engineers out there trying to make the system work,
Engines