Sounds useful!
There is a bunch of product questions around how this could/should work in my mind. It looks like a problem that has been already figured out or solved in other forum software, but I wonder how will this be framed / built around Discourse’s philosophy.
I am also wondering more about the manifestations of providing uploads settings, e.g.: if you chose to introduce extension configuration, the composer needs to cater for this when users are selecting/uploading attachments, and so on. Also, whether this should be in core, or as a plugin.
On the bright side, if we ignore all questions / assumptions / product / design considerations, it doesn’t look like it is technically tricky, I made a one hour spike here (this is very immature implementation though 
).
You can definitely extend this with a bunch of useful features: settings, search / filtering, sorting, etc (and some other considerations like supporting pagination, …)