wimlib

Is it possible to dump files from incomplete wim files ?
For example, run wimlib capture to create a wim file and terminate wimlib during the process.
This creates a broken wim file but it should contain some files of the original directory.
It seems that metadata of these files are missing.
Is it possible to dump the raw files out of the broken wim?

No, this isn't supported.

You might be able to recover some file contents using a custom program, but all metadata is written at the end of the WIM file. You'd basically just have the contents of random files concatenated to each other, without any information about which file is which and where each file even begins and ends. Also some would be compressed and some not, and that might be hard to distinguish.

So the hardest part is to find out the beginning and end of each file, and its compression algorithm?