This could be a good feature, as staff must have an ability to upload files of any size – regular users not. There is already an option called authorized extensions for staff , so why not add an ability for staff themselves to control size of uploaded files or make it unlimited?
Also, would that be possible for uploads.json?client_id=000000000000000 also set some additional param that would always be the same for the given user (disregard of session), so perhaps it would be possible to differentiate the size of uploads for different users (staff vs regular/unauthenticated), so on webserver side we could define client_max_body_size (or whatever) based on location (which considered query as well)? So Discourse upload query would look like uploads.json?client_id=000000000000000&user_id=constant_hashed_user_id_string.
In short, we need to have an ability to upload larger files, like share beta version of our software with specific people (for testing) but users almost never need more than 2M.
Thank you for fantastic software and making the world a better place! <3