The easy solution—which in fact is not ruled out by the quoted policy announcement—would be for all existing baby bonus payments to stop on March 1, 2014. Rather than creating a payment cliff of $3,000 on that date, this would create an (almost) smooth gradient over 6 months starting in Sept. 2013, since the baby bonus is paid in 13 fortnightly instalments. Problem solved.
It is a great solution and also politically viable too as the impact of the baby bonus payments stopping would only be felt after the election. This is what a broad imagination buys with economic policy.