I had to actually do something like this. Due to the hilarious nature of the business, getting an S3 account to use for 'local' (i.e. dev machine) development

I had to actually do something like this. Due to the hilarious nature of the business, getting an S3 account to use for 'local' (i.e. dev machine) development was a huge chore. We wound up creating an Interface to abstract our usage of S3, and wrote a 'local' provider that just used the local filesystem. Of course, many use cases that would not work.... But the big -advantage- of it was, we at least knew that if we ever wanted to switch away from S3, it wouldn't be hard. The Interface had a spec that could be used to ensure that any plugin would work with our application's usage. It wasn't -that- much more work.