In 1993 Mark Waugh opened the bowling in an Ashes match
I think that many all-rounders are 'discovered' by chance, because international teams are desperate for them to balance their sides. People thought to be no better than medium pacers are suddenly encouraged to run in a little harder and it's suddenly discovered that they have the potential to bowl at serious pace (Craig White and Flintoff are both examples of this). Or you have people like Jayasuriya who are promoted up the order in ODI games, and to everyone's surprise have the potential to become seriously good batsmen. Basically until people are given the responsibility of doing either discipline as something other than a part-timer they won't apply themselves properly to reach their full potential.
Aus strength in recent years has counted against them. They have just been too strong in both batting and bowling to ever need to experiment and discover people by accident.