I'm not aware of any planned/possible way to do copy exactly as you would an HTML page with HTML tags, but there's a big project to make selection and copying much simpler and more powerful (design doc [1], in progress PR[2]).
With that PR it should be easy to just add one SelectionArea to the root of your app in order to make everything selectable, like it would be on a web page. You don't need SelectableText widgets. There's an example of this in the PR [3]. No built-in support for multimedia or rich text copying yet though.
Text input fields should already do copy/paste pretty much the same as native.
We ended up having to duplicate some of the functionality of Raphael ourselves while writing the processing mentioned in the article (like to locate regions of an uploaded image after transformation). We thought it was best to just use this code to do the layout as well. It also ended up being a lot smaller than a full library, since we're not using a ton of features.
That said we played around with Snapsvg, and it is great if you're lucky like us and don't have to support IE6.
Thank you Mark! We were actually originally using Raphael but recently switched to something custom. We got a lot more performance for our use case. I would love to open source that code at some point.