Hmm ... that's an interesting idea. My impression is that adding a separate property to SOAPProxy might be a bit funky, but that's just me. David is best qualified to address that.
Generally speaking, I like the idea of having a single way to reference JBossWS hosted services across ESB actions. If we end up creating more confusion by changing the SOAPProxy config, however, then it's best to just fix SOAPProcessor and leave SOAPProxy alone.