I realize Google Drive is vulnerable to the same legal arguments as Mega, the idea is that multiple sources of download are more robust than one. Currently, I don't have the time or knowledge to manage these files, I don't even know if the current file hierarchy/file contents will remain the same, that is why I defer to the subject expert, which seems to be only you.
I'll take up your advice and ask the 07thMod team if they want to host the audio files.
The files I have uploaded work as a simple file swap for everything except Tsumihoroboshi. I was playing through them all but got busy with work and haven't started Himatsubushi yet.
* For Chapters 1-4 you just replace the BGM/SE with those marked as "Question BGM/SE"
* For Chapter 5 you just replace the BGM folder with the one marked as "Meakashi" BGM, and the SE folder with the one marked "Answer SE"
* Chapter 6 requires script changes, alongside BGM/SE replacement, as they outright changed what BGM is called in the scripts. I've modified the scripts, but I have not gotten around to testing them yet. This must be handled via scripts, because multiple BGM had their calls changed to the same BGM post-update. The BGM itself is the same as Chapter 5 with a few additional/changed tracks. The quickest way to handle this was to use Chapter 5's BGM as a base, and to then copy the Tsumihoroboshi BGM into the same folder, overwriting as necessary.
* Chapter 7 follows the same format as Chapter 6, building off both Chapter 5 and 6's BGM and "Answer SE". You'll want to copy the "Minagoroshi BGM & SE" into their respective folders. They basically did song replacement the same as Chapter 6, but since Chapter 7 was not released pre-update, there were no script changes. The BGM files themselves were what was replaced, by taking a BGM, renaming it to a different BGM, and replacing that BGM with the renamed version of the other BGM. Basically, they already had a copy of the song, but they chose to effectively remove a song in favor of a renamed version of a song that's still in the folder. In short, restoring the BGM to pre-update yields some BGM/SE replaced with others. I just renamed the few changed ones that mattered to get them back to what they were supposed to be.
As for 07thMod, you'll probably want to use the BGM Revision Channel, at the bottom of their channels list