Dear Mamta,
You can give Medical Leave Extra as well, that all is management call. Yes when extra leaves are entitle, employees keen to avail most/all of them in a calender year. Moreover, leave on medical ground can't be predicted, so you can't bound them to intimate in advance or have prior approval.
There could be two scenario, if you don't want to take extra financial burden, you can bifurcate the existing 12 leave into 5 & & (being Casual & Medical). But as specified you want to give separate leave, but due to 'timely delivery" can't allow/afford all/most of them at a certain point.
You can draft a Holiday, Leave & Rest (Weekly off) Policy. I would first suggest to allow Weekly off as per rotation basis (for which you have to draft some home work that how much minimum employee you need on daily basis, consider their duty for 6 days in a week, count the total mandays required etc).Once you overcome with the required nos, you can mention the below points in your policy:-
In case any Holiday is appeared on W/off, no Compensatory Holiday will be allowed.
No Holiday will be allowed between continous Leave. The individual must be available either before or after the Holiday. Else the same will be counted as Leave/Absent.
Norms for taking Casual-Sick Leave:-
1 Maximum 2 Casual Leave can be availed in a single instance, beyond 02 regular CL, PL, if any, will be adjusted. If no PL in balance same will be deducted.
2 Maximum 3 Sick Leave can be availed in a single instance, after that Medical Certificate to be produced to the HOD.
3 In a single instance, either Casual Leave or Sick Leave can be availed, beyond the maximum limit PL, if any, will be adjusted
4 No W/Off-Holiday will be allowed between continous Leave. The individual must be available either before or after W/off-Holiday.
Else the same will be counted as Leave/Absent.
5 All leave should be first pre-approved by the supervisor/Shift Incharge and must be finally approved by the HOD.
6 Repeatition of Leave around the Holidays & W/Off, is allowed only against prior approval from the HOD.
III WEEKLY OFF POLICY
Norms for W/off Policy:-
1 In general the W/Off (Weekly Off) is allowed only after performing 06 days duties (Present)
2 In case any W/off is appeared on Holiday, no Compensatory W/ Off will be allowed.
3 No W/off will be allowed during consequtive Leave/Absent/Holidays.
4 For availing the W/off the individual must be Presented either before or after the W/Off. Else the same will be considered as Absent/PL.
Hope you will find above as per your requirement. You can make modification as per your management decision and company policies.