There may be a confusion in regard to waiver in that Siva may be looking at waiver in the context of a breach,when the lease allows the landlord to waive ie decline to insist on something. By asserting the right to waive the need to carpet, presumably on the leaseholder's architect's advice in the application, I can see why the lessee thought that their best avenue was the other tenant.
The arguments against the landlord are more complicated, and, as is the case so often it's about getting "one up" against the offender, not resolving the problem. Something to boast about when one is on the Riviera for the weekend.
Based on the information posted, I offer my thoughts.Any action you then take is your liability. While commending individual effort, there is no substitute for a thorough review of documents and facts by paid for professional advisers.