Well, more like "free extension", but anyway: I got a little toy for you to play with:
You can think of it as an RC. If you're not encountering any flaws (or at least don't let me know about them ^^), it'll get published on Monday.
Here's the changelog:
new: context menu entry for opening supported links with Documents (Opera 12.10+)
new: title of the document is displayed instead of its file name at the right side if available
new: high resolution icons (for Retina displays)
fix: save button behavior not in line with original buttons
So happy testing 😉
P.S: The translations are vastly incomplete. I'd appreciate anyone who'd like to give me a hand!