In my view, you should follow leave policy as defined and applicable to three distinct set of employee ie Factory, Shops Act and Sales promotion employees.
The Acts provide for minimum conditions and you have scope to better it later when needed.
In respect of the 60 members of production staff and 20 of administrative staff working within the premises of the Manufacturing Unit registered under the Factories Act,1948, the leave provisions of the Factories Act would be applicable.
All the administrative staff employed in the registered office at the city of Ludhiana would be covered under the State's Shops and Establishments Act and as such so are their leave too.
Among the sales staff, those who fall under the definition of "Sales Promotion Employee" u/s 2(d) of the Sales Promotion Employees(Conditions of Service)Act,1976 would be covered by the leave provisions of section 4 of the Act. You can find the various kinds of leave applicable to SPEs, their scale,method of sanction, encashment etc., in the SPE Rules,1976.
Therefore, your leave policy should comprise of the leave provisions of the FAct, S&E Act and the SPE Act,1976 in respect of the catergory of the employees falling under each of them.