yeah, i've thought of numerous what ifs
including a civil war between clone and clones
That kinda happened in the 'Rise of the Empire` section from Star Wars Battlefront II
Granted you're playin as Stormtroopers, but you are still a clone and youre fightin clones.
It was this battle that made the Empire recruit men and cloning them rather than cloning one man (Jango and Boba Fett) to make an army as they were too "open to corruption" or something.
Try looking on Youtube for gameplay of the 'Rise of the Empire` Kamino level and you'll see what I mean