This looks like a modified UE4 pak-file, but with LZ4 compression. Luigi's script doesn't work, unfortunately. Luckily, the TOC seems pretty easy - it's in the end of the .pak, after each name there is a pointer inside the pak. Each chunk has 21 bytes header with compressed/decompressed size. In TOC there is a list of chunks, they also look like starting/ending hex offset or size.
The largest .pak is 35 GB, btw.
My BMS skills are too mediocre to write a parser/extractor, so I hope for help of this community.