Fluffy Bunny
Just to take one of these aircraft G-DEWR it was sold by the MoD in 1990 and repaired under the BGA airworthiness system pre EASA. The BGA system was considerably more lax back then when it came to paperwork and took a much more practical approach as was the usually the case twenty-five years back.
The fact that these aircraft might form a way of using grandfather rights to get the aircraft onto the civil register could be investigated however regulatory oversight has moved on in twenty-five years ( for that you can read got a lot worse for little or no flight safety advantage ) would make the the task of moving the aircraft to the civil register a difficult task.
The task of moving the aircraft back to a Grob type certificate would require the sort of oversight that the RAF is now performing and the agreement of Grob, ask your self if you were Grob what is in it for you ? Perhaps 80 gliders flooding the market and trashing any chance of new glider sales ?
If I was Mr Grob I would leave well alone.