"Anything associated to a Project" would be a poor experience, in most cases. I think deliberate file storage for Projects is what you're specifically wanting?

More on the usecases:

• We often have meetings on the phone where someone writes a log/summary and sends the file via email. It would be great to be able to additionally store these logs in Phabricator.
• Many of our projects start with an application for some funding, then receive an approval from the ministry, and then regularly send reports there. We would like to store them easily accessible in Phabricator.

We did that in Redmine before: We created a "document" with a short description and attached the file(s) (usually PDF or ODT) there.

I personally think that embedding (links to) the files into wiki pages is great. But on the Files backend this creates a jumbled dump of files, which makes it difficult to find a file that you know must be on some wiki page of #project.

• I could imagine tagging files to order them - that would allow to easily find them later.
• Tagging wiki pages would also be great - e.g. to create a bidirectional link between a project and its wiki pages.
• If a file that was uploaded by dropping it onto a wiki page (as in: drag & drop) would automatically be tagged with the tags of that wiki page, that would solve our problem.

Wiki page tags would be passed on to pages further down the path. Moving a page to another location would retain the tags and apply any new ones from further up the hierarchy.