when we started building the Reality Editor, we also started to experiment with unity 3d as well. But there is a important concept you have to understand, which eventually lead us to web technology as the foundation.
Think about unity 3d as the flash player from adobe and the reality editor as your web browser.
What you want to archive would be to implement a web browser within the flash player which is a plugin for a web browser. Putting a grown chicken back in to an egg.
You will not only need to implement networking capabilities and in time content loading but also some kind of authoring language for transporting that content.
Unit 3d is a single user game engine that can export to html5.
The reality editor is a web browser that enables the web in to the physical world.
Two very different things.