Isos have to fit on a blu-ray disc to be sold physical, so they are both heavily compressed and also to be honest the game looks like shit on 7th gen. Pc has had an HD texture pack (I believe optional when you own the game legally so probably an option in the installer) and it's true that there is a lot of content in newest version that is online exclusive but you will still be missing on a ton of sp fixes.
Lol what? The download and the game size are two different things. The repack is "compressed" thus occupies a lot less space than the game when installed
It's not going to work out well it is complicated to do that and even the PlayStation 3 version is awful you must skip missions where you must dive in water it's pretty bad of all emulators.