This is excellent, really good work. The whole MSX tree has been crying out for some (knowledgeable) attention for years.
Unfortunately, I'm also the bearer of bad news since there are some issues:
The DATs haven't been built 100% correct. You need to disable the extension being added for both 'name' and 'description', it should ONLY appear within 'rom' field. Also, you need to include CRC32, MD5 and SHA-1 hashes.
I assume you're using ClrMamePro, if so I have some Dat2Dir templates here that you can use:http://www.redsplinter.com/tosec/TOSEC%20(multi%20files).d2dhttp://www.redsplinter.com/tosec/TOSEC%20(single%20files).d2d
though you will still need to manually copy&paste (then update) the header.
The new categories are great, the old deprecated 'Various' category should no longer be used so this is perfect. Unfortunately, what's also depreciated is having 'mixed' file types per category.
So, for 'MSX MSX - Applications' for example you currently have a mix of '.dsk' and '.cas' files. These need to be separated into two DATs (or more if there are other file types), i.e. 'MSX MSX - Applications - [DSK]' and 'MSX MSX - Applications - [CAS]'. This split/DAT naming is only applicable if there are mixed file types.
For example 'MSX MSX - Firmware' only includes '.rom' files (as far as I could see) so it should remain 'MSX MSX - Firmware' rather than 'MSX MSX - Firmware - [ROM]'. Make sense?
Because of issue number 1, when I ran your new DATs through our TOSEC 'DAT validation' tool it flagged all images as having issues so I wasn't able to check for any specific TNC errors. It suddenly occurred to me you may not have been given/have had explained this tool. The latest version (as well as historic) can be found on our FTP under '/tools/tde', otherwise I've also mirrored the latest here: http://www.redsplinter.com/tosec/TOSEC%20Dat%20Explorer%20v20120225.rar
You can load individual DATs to display, or it can bulk check an entire folder of DATs for a multitude of errors/issues (File->Batch Job->Check Folder). I would recommend using this tool to check your DATs once #1 and #2 are sorted since it can flag up any issues that need correcting.
Hope that's not too disheartening, I can see already that a huge amount of work has one into this all ready (well done all round BTW!). Once these couple of issues are sorted, we'll be golden....