We've added this functionality to jboss-classfilewriter: https://github.com/jbossas/jboss-classfilewriter/pull/4. Once 1.0.6.Final is released we're ready to add method signatures to proxy methods. We also consider making this configurable so that it's possible to disable this in some edge scenarios.

Well, there is a marker interface already - org.jboss.weld.bean.proxy.ProxyObject. But it's not part of the Weld API and should not be used outside the weld codebase.