Of course it won't boot if you put PSP files in a PS3 game structure.
I was checking the PSP Launcher from Cobra, and first thing I noticed is that the Data Type is 'MN
' in the PARAM.SFO
Inside the USRDIR, there are two files and one folder: ISO.BIN.EDAT, MINIS.EDAT and CONTENT.
Inside CONTENT there is a EBOOT.PBP, which I guess is a hacked loader that I presume requires the Cobra dongle connected as a security measure.
Decrypting the EBOOT.PBP, reversing the ELF and recompiling it again with any security measures removed, then it should make possible to execute some ISOs of PSP minis. This is obviously not an easy task
~ Dreams and dedication are a powerful combination.
... multiMAN is a perfect demonstration.