Your response is very well thought-out and presented, Chris. And in fact I agreed with it before I saw the early episodes. Prior to my viewing the early eps, I was exposed to the view on this forum that Elizabeth was Vicki's mother. I was doubtful primarily because I just didn't see any indication in the relationship and interaction between them -- especially on Elizabeth/Joan Bennett's part -- that would give any indication whatsoever that Elizabeth was Victoria's mother.
What opened my mind to this possibility (I wasn't a fanatic convert) was seeing several subtle hints in Joan Bennett's performance in the early episodes, along with some visual clues such as Elizabeth coming down the stairs with her hair down like Vicki's, and before she comes clearly into view, she looks identical to Vicki. I believe there were a few other hints, too.
Add to that Joan Bennett's testimony at one of the festivals that she played Elizabeth believing that Victoria was her child, and also the fact that Dan Curtis Productions authorized this revelation in the recent DS novel "Dreams of the Dark."
I also heard of a real-life case that was very similar, which made the possibility seem emotionally possible for Elizabeth (something else I had doubted).
Nevertheless, the case for Paul Stoddard as the father as you outline it is very strong, and I do find it less troubling. So I'm not a hardliner on the issue (though you may find that others are!).
As an aside, in my "signature" line as part of my posting profile, I have excerpted a few lines from the novel "Bleak House" by Charles Dickens, which concerns, in part, an illegitimate young woman's search for identity. The passage quoted is from her meeting with the formidable Lady Deadlock, who she has been introduced to. Her thoughts could be the very thoughts of Victoria Winters upon first meeting Elizabeth Collins Stoddard.
-Vlad