It is not that easy edit PS3 Game Backups for OFW. Even editting sometimes makes the game unplayable, without resigning the eboot.bin, as on the marjority of the ps3 games (and xbox360), the game executable is hashed to the specific game files, so any change on the game files will not allow the eboot.bin (think as the game .exe) run because it will identify a change on the game files. As for hacked consoles, the custom firmware does not allow this check to happen, it runs directly the game ignoring this hashing check. So because this jailbroken PS3 can run game mods, custom maps, and so on...
Hello Bro. Editting game backups, to my humble knowledge, varies from game to game, according to engines. In example, there are some tools to edit textures in the last of Us PS3, however these tools are specific to this game, and the method varies from game to game. Some games may even need to do some HEX editting. Again, editting game backup to run on OFW hardly will work, because, like I said, the eboot.bin is hashed to that specific game files. Some games may even work, but the marjority will not. Cheers.