I love your idea and execution. But requiring yearly subscription is defeating the purpose of "Break away from big tech" as I am now tied to your company instead of big tech. What's the point in this?
Using email as an example, having to transfer email with drag'n'drop in something like Thunderbird is clunky, slow but works to a degree.
Having direct access to the mailbox directory on the filesystem would make it easier to transfer out/in (assuming you already have your emails in the same format).