Perhaps try PPF instead of BPS?
The reason why I considered BPS in the first place is because it seemed a bit more 'popular' like IPS. Not that I really needed a replacement to xdelta, just that it might be more convenient to users with Floating IPS (which supports both IPS and BPS).
PPF would likely work as it was designed for PSX but its a bit of an old and obscure format like APS. Not really supported by popular patching programs (it's a nightmare when you encounter .aps or .ppf and have to track down the right app!)
Xdelta at least has some maintainers on GitHub, but the program has a solid pedigree and is well documented and open source.