Well, at long last, here it is! These are listed in no particular order. Feel free to add your own suggestions in the comments.
Portillo's is a political journey that would make fascinating reading. He probably thinks is too early to write his testament, but he shouldn't leave it too long. Every one has a shelf life.
Lord (Robert) Armstrong
Has been around the centre of power for forty years. The convention that Cabinet Secretaries don't write memoirs should be abolished. He would provide a fascinating insight into the inner workings of government.
Lord (Robin) Butler
Would probably need a ghost write to keep the text below a million words, but nevertheless his story would be worth telling. I suspect it would be laced with emotion and bitter regret.
Having written seven volumes of diaries you might think there wouldn't be much else to say, but an autobiography is a very different beast to a spontaneous political diary. It would provide perspective on one of the longest careers in British politics.
A strange inclusion in this list, you might think, yet John MacGregor was a Minister throughout the entire Thatcher and the first four years of the Major government - and a Cabinet Minister for nearly a decade. I've been encouraging him to put pen to paper and haven't given up yet!
Britain's leading political adacemic started life as a journalist but has become a world authority on the inner workings of government, and he has a fascinating life story to tell.
Ashdown's diaries do not tell the whole story. His post political career in the Balkans would add a lot to his story of a politician who rose from nowhere to become a key figure in the revival of the Liberal Democrats.
Charles Powell was for some years possibly the closest adviser to Margaret Thatcher. His foreign policy insights during the period which saw the end of the cold war need to be written.
I'm cheating here a little as John Biffen has indeed written a memoir which he was completing just before he died. I was trying to help him find a publisher and I hope that will still be possible. Having read an early draft of the manuscript his pre-political life is just as fascinating as his political career, where he distinguished himself for his honesty and candour.