Customs on GH3 360 Main Setlist ?

I have a RGH 360 and I'm well aware that one can add custom via Onyx to the "Downloaded Songs" in GH3. However there's a limit of aprox 70-ish songs.

My idea is to be able to replace the main setlist songs to custom ones, similar to many PS2's custom ISOs. That way we could increase the max limit of custom songs on console.

I've seen people porting PS2 custom isos to 360 (like GH Brazukas), so maybe there's a tool I'm missing on.