Colleagues, I would like to ask: who, in fact, will be involved in promoting this dat and who will adding info there during it's lifetime?
It will be a very-very ambitious work, but what will be the result? What will this additional dat give you? Header is a very vague phenomenon, there are several variants of alternative files with different headers.
You can take the last GoodNES as a basis, but it is already morally outdated. You can take more modern files in iNES 2.0 format, but why we need to duplicate them in our database, when they already perfectly exist in their original form (in various original forums)?
From a practical point of view, creating such an additional dat makes little sense, but the work will need to be done enormous. It seems to me that you better make a corresponding request to the emulator developers. Let them write their software more correctly, that the definition of ROMs was made correctly without using headers. For Super Nintendo and Sega Mega Drive, a lot of emulators have been working without headers for a long time, everything works fine. Why is Famicom worse?
As for me, I will not devote my time to this dat at all since there is still a lot of other really useful work on DoM (in which you may also be involved