Makes no sense to me
I don't get the whole binary XML thing. Sure, I know XML is slow but if performance (either size or speed) is one of the primary criteria for your application and broad interoperability is not, then why would you be using XML at all? If you need both high-performance and broad interop, then you need to make some compromises. Creating binary XML isn't going to help much unless it somehow becomes a widely accepted standard because you are going to be back to the 90s CORBA vs. DCOM thing where binary incompatibility crippled broad-based cross platform interop. The beauty of XML is its simplicity - let's keep it that way.