Sorry, i didnt see what chd support is only for genesisplusgx 1.7.5.
I found how to add .chd at the file es_system.cg with putty.
Also i have tested the pbp format with ppsspp with success.
I think you can add this to the next version of batocera.
<extension>.iso .ISO .cso .CSO .pbp .PBP</extension> in the psp section.