I don't think it would have been just the Australians they were worried about, but you are probably on the right track. The Flying Badger sums it up well in his signiture - A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools - Douglas Adams.
Another reason for deleting the hand throttle is dollars. When you make 100,000 cars saving even a few cents per car adds up to a big saving, and with hand throttle being irrelevant to 99% of vehicle owners it was an easy target for deletion.
As long as you can find a suitable mounting location for the hand throttle knob - it needs to have a clear area behind it for the cable, I don't see any reason why you couldn't adapt a GQ hand throttle to fit a GU.
Tony