Guess what? The NAI really did implement a "digitize on-demand" function.
This is just a little update on my National Archives of India post. Judging from e-mails I receive from researchers working in Delhi, a lot of my advice re: accessing NAI collections in person is still true. But the prep stage for research at the NAI has changed a lot in the past few years, as the NAI's digital game has really improved. I added a link to the NAI's online interface to my original post awhile back. Since then, I've discovered the Abhilekh Patal portal, the newest entry point into NAI collections.
The first place to start with the Abhilekh Patal portal is the "5 Step User Guide," as it tells you how to sign up for access and structure searches (you need an account to see the digitized material). Once you're signed up, click the tab for "Digitized Collections".
As you can see, they started with the big guns — Gandi, Kassturbhai Lalbhai, S. C. Dixit. The Cartographic Records section is growing. Delhi maps outnumber maps of other cities/regions, but there are a lot of Punjab and Tinnevelly maps as well. Lucknow, Hyderabad, Peshawar, Hoshiarpur ...
The biggest digitized collection falls under the heading Public Records. Some data entry errors make it seem like they date back to 1551 AD, but those records are really from either 1851 or 1951, depending on the document. We're mostly talking late 19th-century into the 20th (i.e., colonial era) material here.
The tab for "Online Reference Media" seems to be an catalogue for all digitized material.
Anyway, this should give you a good idea of some of the holdings of the NAI — useful for writing your research proposal/grant application.