In the times where people had to use ODEs for super slim PS3s, there was a program to resign the ISO and its updates and bake it together into one large ISO.
Iirc the creator of the tool was Rudi Rastelli, but I didn't find it anymore after a quick search.
It didn't work well to begin with, it's really easier if you just buy an HDD to upgrade your internal storage.
I spent so much time on those tools back in the day and in the end it was just wasted time now that PS3HEN has brought all relevant features to all PS3s.