Unless there are legal concerns between Bungie and 343i that somehow go beyond the current agreements, I don't see how grandfathering couldn't have been an option. This is all just information in a database. And grandfathering would only require a simple query that referenced the data that they already own and have possession of. If I couldn't click on my profile right now and view my Halo stats, then I would tend to lean more toward the position of "it's probably just not possible". But the info is there. Bungie has it on their servers, within their databases. So this means that there are zero technical limitations in this situation. And I seriously doubt 343i and Bungie came to a legal agreement years ago that said "Okay.. Bungie gets to keep all that data.. but they can't use it for anything but legacy stats and avatars". That just doesn't make sense to me. I'm sure they had their reasons for this decision, but it wasn't because they couldn't do it.