POGS when you say The clue is in Prime Ministers Questions you are right - they are questions to the Prime Minister which does not seem to dictate how the Leader of the opposition should use them.
As I have said earlier in this thread PMQs have changed a great deal and there is no reason why they shouldn't change again. Personally I think the minister from the relevant department asking the questions would be an interesting and possibly enlightening change. This may be of interest:
Although prime ministers have answered questions in parliament for centuries, until the 1880s questions to the prime minister were treated the same as questions to other Ministers of the Crown: asked without notice, on days when ministers were available in whatever order MPs rose to ask them. In 1881 fixed time-limits for questions were introduced and questions to the prime minister were moved to the last slot of the day as a courtesy to the 72-year-old prime minister at the time, William Gladstone, so he could come to the Commons later in the day. In 1953, when Winston Churchill was prime minister, it was agreed that questions would be submitted on fixed days (Tuesdays and Thursdays).
A Procedure Committee report in 1959 recommended that questions to the prime minister be taken in two fixed-period, 15-minute slots on Tuesday and Thursday afternoons. The recommendations were put into practice under Harold Macmillan during a successful experiment from 18 July 1961 to the end of the session (4 August). PMQs were made permanent in the following parliamentary session, with the first of these on 24 October 1961.
The style and culture of PMQs has changed gradually over time. According to Speaker Selwyn Lloyd, the now famous disorderly behaviour of MPs during PMQs first arose as a result of the personal animosity between Harold Wilson and Edward Heath; before this PMQs had been lively but comparatively civilised. In the past, prime ministers often opted to transfer questions to the relevant minister, and Leaders of the Opposition did not always take their allocated number of questions in some sessions, sometimes opting not to ask any questions at all. This changed during the premiership of Margaret Thatcher, when the prime minister chose not to transfer any questions to other members of her Cabinet, and Labour leader Neil Kinnock would always take his full allocation of questions.
One of Tony Blair's first acts as prime minister was to replace the two 15-minute sessions with a single 30-minute session at noon on Wednesdays The allocated number of questions in each session for the Leader of the Opposition was doubled from three to six, and the leader of the third-largest party in the Commons was given two questions. The first PMQs to use this new format took place on 21 May 1997.
en.wikipedia.org/wiki/Prime_Minister%27s_Questions
I would also like to go back to the "comparatively civilised" PMQs (if we have to have the in Parliament at all) that existed before the Wilson/Heath parliament.