How can I create text-based aliases? (Local hyperlinks?)
I'm not aware of any way to do this without 3rd-party software.

However, you can definitely do this with OmniFocus.

You can "attach" files, but have that attachment simply be a "link" to the file, so it's not actually moved inside your OmniFocus database, it still exists on your filesystem.

Then your reminder/to-do could be something like "Review Quarterly Report" and have that report attached as an OmniFocus link.