While this type of service may not work in the United States, in India, where much of the population lives according to strict religious dietary practices, it may end up being a booming success. McDonald's will open two veggie-only stores, one in Amristar (the holiest site in the Sikh religion) and one in the town of Katra (an access point to the holy shrine of Vaishno Devi.)
The change to veggie-only restaurants will not be a huge change as the company had already decided not to serve beef because Cows are considered to be sacred in India... thus instead of the Big Mac they have the Maharaja Mac, which includes chicken instead of beef... the step to eliminate all meat was just the next logical step.