@JFX My apologies for even asking, but I would really like to know if you might be interested:
Is it possible to allow installing Windows from a RAR file (WinRAR Archive)?
Basically the RAR file format's story is that it's a full backup format that supports saving all NTFS attributes, timestamps and ACLs, etc.
Using WinRAR's unrar program allows for very fast extraction of big archives (multi-GBs) while restoring all NTFS attributes & properties.
So I could for example use ImageX to unpack a sample install.wim file from a Windows ISO to a scratch directory, then archive it as RAR5 with the best compression settings, BLAKE2 checksums, preserving timestamps and NTFS security permissions (ACLs).
This would help to create a sample install.rar file that cans also easily be split into arbitrarily-sized parts (e.g. 700MB parts, 2GB parts, etc).
So finally for installing Windows, what you would do is to properly select the desired install partitions and extract the RAR5 file to the Windows partition you want.
Of course I understand that you have to run WinRAR (for archiving) and WinNTSetup (for install) as TrustedInstaller to do this, but we have many tools made specifically for running programs as TrustedInstaller (example: 'RunAsTI').
So, is this something that you might consider doing in the future?
Or perhaps you might think that it's not necessary to work on such an idea right now, because .wim files are good enough?
I would also like to add that RAR4 & RAR5 archives can also possess recovery records, which help automatically correct errors if part of the data is damaged (with configurable percentage of recovery record size).
Of course I understand that if you do it, then it would only support RAR archives without a password.
And I also understand that the usage of such install.rar files would be mostly useful for creating 'super-small' ISO files.