I\'m attempting to implement a delegate Service provider by overriding the bean definition for the original service with my delegate Service. However, as the name would imp
It sounds like you're trying to reinvent spring-AOP. Please consider using spring-AOP for this.
It's possible to programatically change the name of the existing service and create a new bean with the old name. The autoproxying-code inside spring framework does this and you could have a look at that. A quick code search for AutoProxy* in the spring framework should get you there.
Alternately if you control the client sites (the consumers), you could add a qualifier to your wrapper, and use qualifiers to coerce the proper implementations to the consumers. The the wrapper could use the unqualified implemementation to get access to the original. (It might also be possible to retro-mount a qualifier to the original implementation by adding another bean definition for service with a qualifier in xml code that you control, haven't tried this but it should work)