This comes close to an opinion question, but I hope that someone can give a definitive answer.
I have written a game app and I save game data locally. But I also will want it to be cloud capable and I am currently writing the code but I keep hitting a mental barrier. In several places in the iCloud and Game Center documentation it says if I change Apple ID, I need to delete the local save game data/file cache. This is contrary to how my app currently works, which is OK if I can figure out the right way to do it. In the ICloud documentation it says to either user the cloud or don't use the cloud and only ask once, but there is a button in the settings to turn the iCloud Drive on and off.
The core of my dilemma seems to be that an IOS device is not tightly linked to one Apple ID. I understand that multiple devices can be associated with one Apple ID, but not why it should be true the other way around.
This can be seen as either added capability or enough rope to hang oneself. As a user I can, using my Apple ID, get on to another device not associated with my Apple ID and:
download an App/Song
log into Game Center and play a game we both own.
etc.
I know Apple deals with this and now I have to do the same.
As App Developer I see a world of questions about what this might mean, like "Well I'll do this or that but what do I do the first time this other thing happens?", etc.
For example, initially I thought I could consider "local" store the same as a very long airplane mode, and when the cloud became available I could sync the delta to the cloud and across devices, but this does not address changing Apple ID. Do I blow away the local data, keep the new user from playing the game, only allow local or cloud but not both?
Now Apple is adding Multitasking, and a login to iPad's used in schools, the problems become even worse.
I keep trying to find some profundity that will steer me to the correct answer but I am at a loss on how to deal with Apple ID changes.