The primary question here is even if the Employer permits your friend to work on week end, what he is going to do in the absence of all other employees who will be weekly off ? You have stated that your friend is in a senior leadership position which literally means that he is in a Supervisory position overseeing the operations of the office ?.
There is no such provision in the law to accumulate week off and to avail it later. It is at the discretion of the employer. Due to exigencies of work requirement if employee work on week off he will be eligible for double wages and one comp-off which he avail later. Your friend being in a senior level (Manager category) I don't think his employer opt him for comp off facility which is a commonly followed practice among private sector companies.
More over being in leadership position his presence on week days will be more essential than week off when everyone is on week off.
I suggest he may take leave once in two months or so if his employer permit him to proceed on leave.
From India, Madras