I have two possible solutions to preventing early season injuries.
The first one:
Australia v Australia 'A' in two four day games and three 1-day games.
This would be beneficial for both players and selectors. The players will get a chance to get through some overs or spend some time in the middle, it will also give an indication to the 'A' players who are 'next' in line (although the selectors can often pull someone from nowhere). It will also give an indication to the selectors how the Aussie and Aussie 'A' players are performing.
The second one:
An interstate two or three day pre-season competition.
This would be beneficial for international & state players, selectors and spectators. This could involve each state playing each other once and the top two playing off in a final, then the next year those who played away then host the corresponding team. This would give the fans a chance to see the national players for their states and it would also give the state players some match fitness. It would also give the selectors (both national and state) a chance to have a look at everyone.
Just a few thoughts....