Office of Advocate missing
Altenmann, the research we've done at the Wikimedia Foundation supports what you're saying here -- your description of new people's frustrations is accurate.
I like your Advocate idea, for a couple of reasons. First, lapsed editors have told us that one of the reasons they leave is because Wikipedia doesn't feel sufficiently welcoming or personal: as new editors, they felt isolated, alone, unnoticed. On the flip side, successful editors have often told me that one of the keys to their longevity may have been the fact that they were noticed and spoken with early by a more experienced editor -- someone who commented on their work, helped them do something they were struggling with, or praised them for something they did well. Even interactions that we might define as neutral rather than supportive ---like being taught a particular piece of wiki-syntax, or being nudged towards a helpful policy page--- people have experienced as encouraging and helpful, when they happened one-on-one rather than via a template. People like to be noticed by other people, they like to feel like their work matters, is wanted, and is taken seriously :-)
It's also obviously true that editing Wikipedia today requires much greater policy knowledge than it used to (the alphabet soup that you mentioned). Currently it's tough to edit Wikipedia in part because the editing interface is so complex. But usability improvements won't help with policy complexity. So yes, I agree that one-on-one coaching and hand-holding WRT policies is valuable to help new editors as they get acclimated, and it will continue to be valuable.
Great idea! but why stop there. As a mature society specialization is indeed called for. Why not also reduce the power of anyone to delete or vote on deletions? Create a specialized group of deleters, a police force for wiki that is trained in helpful editing and allow only them to delete and propose for deletion, with special tools at their disposal. Advocacy and help is great, but restrict the power of deletion to specialists!