So let's go through the options here:
While searching around though, I found a great deal of people asking how they force the bar to autohide. It's a common complaint in editorials as well, and seems to be the one constant of all the Safari extensions.
After an extensive search - what you're looking for does not exist at this time :(
Hardly the first time Apple has taken away control from a user, either...
Tl;dr: Apologies, but it's time to let it go - it's gone.
One of the extensions I found is open source and appears to be easily editable. Specifically, this one, and by removing a line of JS, I can force the bar to stay on the screen, and replace it with blank text (so it looks correctly).
Here's the thing, it's still just an overlay on top of the page, it's not a part of the safari "window" as the old status bar could be, and doesn't show all of the same information either.
Here's what the effect looks like
And here's the extension package. You can see the changes made from the official release to make this possible as well.
Installing this requires jumping through an extra hoop since I'm not a registered Apple dev, so here's what you need to do.
- Download and extract the package.
- In Safari, go to Preferences -> Advanced
- Check the "Show Develop menu in menu bar" box
- In the newly added menu bar item, click on "Show Extension Builder"
- Click on the plus sign in the bottom left of the new window and hit "Add extension"
- Navigate to where you unzipped the .safariextension folder
- Accept the security warning
- Reload any open webpages
Usual disclaimers apply, your mileage may vary, void where prohibited, kids eat free, etc.