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What I personally would love to see are two new switched alongside midl.exe /mktyplib203:  

/wsdl – Verifies that all attributes used are applicable to a wsdl contract and then generates a *.wsdl file from IDL

/serviceModel – Verifies that all attributes are System.ServiceModel compatible and then generates a *.cpp file (managed code!) definition Indigo [ServiceContract] and [OperationContract].