Shadow, I think this is pretty...make that very unlikely. It's rough to get many mods working on PSX version, it's even more difficult to get them working on PSP. Like Kaldarasha said, file sizes are important - and injecting the Remastered music into the psx discs, and then converting them to eboots...unless I'm sorely mistaken, you might wanna forget about this right now.
To my knowledge, nobody has attempted to use different music with the psx version of the game.