For those interested, I've been working on a plugin for Xamarin as a pet project for around a year and have put it on GitHub. Anyone who wants to give it a try or contribute is welcome to do so.
https://github.com/MatthewDiamond/MonoDevelop.ResxEditor
Note: There is currently a bug with local paths (e.g "..\Resources\Test.ico") in Xamarin's ResXFileCodeGenerator that can cause issues with most Visual studio generated .resx files. For that reason, the current version doesn't copy resources into the project folder.
