I've been thinking it would be far more useful and cross-platform friendly for OPL (and, to be honest, any other loader on competing hardware) to better support the MAME .CHD format that's been gaining steady traction with emulators as of late. While I've read Acid_Snake's writeup there in that thread about the .ZSO format, I believe .CHD would make more sense to adapt, as that would mean users need only one storage format for their files, whether it be for PCSX2's support of CHDs or for OPL's, and the same benefits can be had of .CHD that are now had with the research done in .ZSO and using the LZ4 compression mechanism.
But I'm just a blob, what do I know?