Yes, some people tried with iso mods I thought but never heard any more of it so I think it's patched or something.
And I think you can't mod the savegame
i saw something about a tool on moddb.com or something like that idk if i find it ill link it to you
EDIT: i found the link idk exactly what this does or what it can be used for but it may come in use to others. if all goes well with this tool let me know! LINK - http://www.moddb.com/games/watch-dogs/downloads/wd-files-extractor