The obvious solution that seems to be overlooked every time sick leave comes up, is to roll it up into ACC, and have sick leave paid out from there, instead of having employers fund it directly.
The sum of costs to employers and pay for employees would be unchanged, but it would eliminate the uncertainty on how many sick days your particular employees take, making life easier for businesses, and it would allow for sick leave to be taken right from day one in the job, making like easier for workers.