> I don't think adding a button or two is some fundamental change

Neither do I, but the change here isn't "adding a button or two".

I get the impression you haven't tried to refactor a large code base to change core functionality before. Any system architecture is built with, inevitably, certain assumptions on how the data is going to come through the app and where it's going to come from. Something as low-level as the source of video files in an app that is no doubt optimized for that is undoubtedly a fundamental change, and one that is going to be easier to fork and rewrite than try to shoehorn into existing code.

In my opinion, default offline vs default online is a HUGE architectural difference. You could probably try to hack it into the existing player, but it wouldn't work well.

A ground-up rewrite wouldn't surprise me at all for such a change.