Weighing up all the options and comments here I think MacDonald would be the best shout. When you look over the years at how quickly young Aussies have come on then it is definitely worth the gamble as all of the candidates out there would be a risk.
Aussies and New Zealanders seem to have speedway hard-wired into their DNA and I can recall seeing a very raw Jason Crump at Brough back in the day and thinking "theres one for the future."
I suppose somebody thought Jason Doyle might be a gamble at some stage.