Unfortunately, the notion of editing an AST is by definition language specific, so it's unlikely that someone could create the structural editor and just have it work for everybody. Moreover, as they mention here for Lamdu, it often requires looking at the language slightly differently and enforcing some rules that wouldn't normally exist in the code. But, with a decent foundation we can at least make writing the necessarily language specific parts relatively straightforward.
For those new to this world and wondering why this stuff doesn't seem to exist, one of the biggest problems with projectional editors is handling the translation problem. How do you reconcile changes in your representation with changes in the underlying code? Can you reliably parse handwritten code into your AST representation write it back and so on without any loss? What happens with handwritten styles that maybe don't fit into the projection's way of viewing the world? What if I know a better way to output the AST than you? It's also particularly difficult dealing with change over time since there are no true unique identifiers for bits of code.
The approach they're taking is likely the correct approach for the "future" - we should be designing languages and approaches to coincide with the ability to tool them. Even better would be to never have a handwritten format at all: the cannonical representation is always the AST. And though you might be able to edit a projection of it as text, you're never at a loss for how to get back to your "good" representation. This is the world I think we ultimately need to get to and you'll be seeing some really cool stuff from us in that vein early in 2014.