Even trying to be "merely" pan-Indic is going to be a problem (as you probably understand better than most of us do). You not only have a large number of individual languages to consider, you have two entirely different conceptions of language (Indo-European and Dravidian), and even if you stick to the Indo-European languages of India, you can't even count on Devenagari. So you have a couple of choices:
1) you can accept content directly for publication, but absolutely require that it be in well-written Hindi;
2) you can accept content indirectly from anyone who can give you content in a language you can easily translate from and communicate in, and communicate with the contributor in whatever language you are both conversant with; or
3) you can make the site bilingual or multilingual.
Option 1 is the easiest, but it's also the most restrictive. Sure, there are a lot of people who have a good working knowledge of Hindi, but the problem with being monolingual is that there's a danger of it becoming entirely monocultural and incestuous. To some extent, any web community is a sort of "echo chamber", but there's a better chance of bringing new ideas for consideration into the mix if you're not locked into a smallish linguistic and geographical community. (And sure, I know that there is, for instance, a relatively large Hindi-speaking community here in Toronto and in other "foreign" cities, but the generation that has a real competence in Hindi is still largely rooted in the culture and values of their homeland. The second generation, or those who have been here since childhood, would be submitting stuff that's as much in need of "translation" as a foreign-language submission.)
Option 2 is obviously going to require a lot more work, but at the same time it can open your blog to a lot more high-quality content, particularly if that "second language" is English. It's not that the English-speaking world has a monopoly on wisdom or any such thing (although it may appear that we sometimes do think that way), but that English (or a broken variant thereof) has managed to become a sort of lingua franca in which people from many different regions and cultures can communicate.
Don't worry that you might need to change the submitted content a bit to make it understandable in Hindi -- every language has its own idiomatic way of expressing things, and it's the mark of a good translator to be able to bridge those semiotic chasms. You should probably make your contributors aware that what appears on your site won't always be a word-for-word translation of what they submitted. It may be a good idea, as well, to engage in a bit of back-and-forth on some of the more difficult idiomatic substitutions -- you may not be able to capture the exact sense of the original, but there may be one alternative that comes closer to the author's intent than any of the others.
Option 3 might sound like a good idea, but there's a chance that Hindi (or more generalized Indian if the aim is to be pan-Indic) might get pushed aside, leaving only the menus and other "chrome" elements behind as evidence of the original site. It may upset the original authors to have their content appear in a form that they can't read, but that's something you'll need to straighten out from the beginning. You can't abandon your audience for the sake of your contributors.
My suggestion would be to go with Option 2 -- accept content from wherever you can get it, but make it available to your audience in clear, fluent, idiomatic Hindi. Come to a licensing agreement with your contributors that allows them to publish the same material elsewhere in the original language if you don't have an alternate-language version of your site. Agree to discuss the more difficult aspects of translation so that you're not putting words in the author's mouth. That will work best for both you and your authors -- your site becomes as useful as it can be to your target audience, and your authors get their original content published as it was meant to be in more than one language. (There is a lot of my content out there on the web that's been scraped and put through, I think, Babelfish and makes less sense than a random word list might have -- and since it pertains to programming enterprise-level software, I hate to think of the damage that was done by following "my advice".)
