The good news if that the forthcoming standard, ECMAScript6, also known as "harmony", contains features to deal with both of these issues.
The latest versions of the V8 engine actually support harmony scoping rules, with one restriction, namely that it's only supported in contexts that are in "strict" mode. I believe that this restriction will go away in due course.
Petr Jelinek dropped me a note that other day to tell me how to set V8 flags, and based in that I have developed a patch for PLV8 that allows for harmony scoping. It requires a new GUC setting that is applied during the module's initialization code.
This is available in my clone of the plv8 code, and you can see what it's doing at https://code.google.com/r/amdunstan-harmony-scoping/source/detail?r=8acdcdabcd0c2b9ad99f66a5258920db805efdc3#
I'll do a bit more testing and then talk to the other PLV8 developers about merging it in.
Things are less rosy on the string handling front, I'm afraid. I have no idea when V8 will get the "template strings" feature that will address the string literal deficiencies. As far as I can tell nobody is working on it.