While it is possible that for speakers of Indo-Aryan languages hindi is probably easier to pick up, that says nothing of the ease of learning the language for the majority of Dravidian language speakers.

The only reason that you advocate learning hindi over English is the ease of picking up the language, which I believe is just plain wrong. The English language is structurally much more free, and easy to pick up than a language such as hindi.

That being said, your premise of standardizing one language seems to be resting on the rather flimsy idea that if the majority of people spoke one language, they would speak it well.

A language is (usually) only spoken well when introduced at a very young age, and that seems to be the only determining factor as to whether one particular language should become an Indian standard. (If anything that language should be Sanskrit since it's the most structurally sound language among almost all the Indian languages)