New FSB5 Tool by snakemeat at 10:35 AM EST on January 6, 2017
Still trying to test it, but others may have more luck (or time). Looks like it may extract OGG without converting to WAV. See here: https://github.com/HearthSim/python-fsb5/.
Yeah, I did the same, I also used it on Transistor's music as that also uses OGG-based FSB5s. It is much nicer than the other FSB5 vorbis extractor out there, that one couldn't handle Transistor's music at all.
It has been a while since I messed with it, but I believe I first manually (maybe?) extracted the FSB5 out of AudenFMOS_Music.bank, and then after that I used my fsb5_split program to get all the files in the FSB as separate FSBs. I then used python-fsb5 on those to get the OGGs. I just haven't done anything with said OGGs yet since Transistor merges multiple FSBs while the game is running.