FPS4Dumper, a later version?

[Barubary]

Those files are most likely compressed. There's a single byte at the start for some purpose, followed by the file size (add 9 to include the/this header), and something that could very well be the decompressed file size. Peculiarly, the endianness of the two sizes are again different from the one used in the FPS4 file it came from. =/

Unfortunately, there are several other projects I want to (and need to) work on first, so I'll not be able to work on figuring out the rest of the format (at least for now). =(
You can try asking the people at Xentax though.