Unpaid sickness leave deduction calc

The calculation that the system uses for unpaid sickness deductions is based on paying the number of days actually worked in a month (based on 1/260 per day) meaning that deduction values for one day sick can vary hugely from one month to the next. For example, in a 21 working day month you would be paid 20 days (out of your average 21.67 days which is one twelfth of salary) compared to a 22 working day month where you would be paid 21 days (thus losing just 0.67 of a day).
We deduct sickness in arrears and have always deducted 1/260 per day absent. However, we have identified that if you deduct sickness in the month that it occurs on paycircle, and the employee has 4 or more days sick, you can choose the option to deduct based on our method rather than the system prescribed method.
As a result, we know that the base calculation is already set up in the system. And we would request that this option is available for any unpaid sick absence regardless of the dates and number of days missed.