Isn't the point of having versioned API's so changes can be rolled out w/o breaking a much of applications at once? Why not increment to version 2 and replace all ID's as strings in the JSON format? Keep version 1 around for a few months
allowing everyone to upgrade and then kill it off. This can also give twitter a chance to make any other breaking changes.
If Twitter is never going to take advantage of the versioning they added what is the point of having it?
I think just creating new fields to avoid versioning issues is unclean and messy.