I read a column on sharing types between web services at
http://msdn.microsoft.com/library/en-us/dnservice/html/service07162002.asp

Sharing types can be acheived, similar to what described here in this
article but little defferently, by defining these custom types in a seperate
assembly and importing that assembly at the top of the proxy generated and
then manullay deleting the redefined custom types in each proxy class.

But still this process even gets worse when there r any updates to any of
those web service implementations and have to update all relevent web
references. Is there any better way to do this automatically importing the
custom types assembly rather perform these manually steps?