I have heard that Euro II mehrans start to create problems when altered in any form, like installing cng and sometimes aftermarket AC installation.
I have personally come across a 2014 E2 Mehru that has become a headache after installation of CNG, the owner has even changed the ECU but car is not stabilizing.
Also saw a '13 E2 VXR standing at AC workshop for compressor change, when asked the shop keeper why the owner didn't claim in warranty. He told me that the company rejected warranty claim for compressor as according to them the culprit was CNG installation
With such stories I don't think its worth risking with any kind of alteration during the warranty period.