Just to throw in a suggestion, I would like to see an addon plugin that filters the allowed filetypes for Supporter, Upgrades, and Membership.
For example those who haven't purchased anything can only upload image and text files. Those who pick up an upgrade can upload larger files and/or video files.
I know it;s come up a couple of times, including once recently. I took a shot at it but was only able to create a filter on the person, not on the blog. Just making it a formal suggestion.