Onto what you've said.
I really hope they plan on using the original pack in this no matter what. i've said this from the start--in fact i thought they might even be involved after that little show first aired. We REALLY need to know what that damned birthmark means; it belongs to a VERY specific wolfpack in New Orleans (possibly the one that had a run in with Klaus's family so very long ago--also explaining why he hunted them without mercy...). Was this wolfpack (as I said in the parentheses) originally from around Virginia, Mystic Falls...?
Also, since we now know that the Originals DIDN'T get rif of all of the wfite oak trees as there was at least one still remaining in Mystic Falls until it was made into a bridge...this could quite possibly mean they have their own stakes from that tree (from branches they used and allowed the tree to keep living) or even far worse for Klaus and his family, they got hold of just one seed and then planted it down near New Orleans. This may mean not only do these werewolfs have possible white oak, but some locals may as well like: any other werewolfs (or Original Pack), witches, humans, and vampires like...Marcel who for some unknown reason seems overtly confident around Klaus when he absolutely shouldn't.
As I said, i think they want to take the shows in different directions... The fact they have already seemed to make Klaus's wolf side an issue and used Hayley a wolf with a "special" birthmark that Klaus seems to have a history with to be the one the witches use for their plot or blackmail, depending on what is really happening.
We have no idea, considering what magic can do when we consider this last season of Vamire Diaries and Silas's abilities (and magical knowledge too), just what exactly the witches have unleashed or have planned for Hayley and Klaus. I actually think the baby is none other than the witch that casted the spell on Hayley in the first place (the one that caused her to black out, surrounded by one of two groups--OR even both at the same time, which is what I'm pulling for--witches and or werewolfs): Jane-Anne. When she cast the spell was she in an extremely large circle during it (all the people that "met" Hayley); can Marcel possible not detect a spell circle or even more to the point the intesity of it as well? I believe the child will be a literal reincarnation of Jane-Ann (another reason the sister is going along with this, and POSSIBLY a clue that their "blackmail" is completely and utterly a "poker face" stunt...she will not get her sister killed twice if true. Since Jane-Anne KNEW she would die due to Marcel and his flunkies they resorted to an extremely unique, daring, manipulative, and hopeful plan. Somehow it may be even possible that the baby IS Klaus's due to the energy involved (especially if she got the power of other dead witches from somewhere else or if like they said, "The spirits wanted this as they are looking for balance in nature, so..."
Then add in some of your details and plotlines and this thing would get amazingly complex.
We'll need three episodes or so to get an idea of perhaps where they wish to put the power at. But, I very much do think that there is no doubt that an extremely strong werewolf contigent (or smaller, basically The Original Pack in that case and Hayley's pack too at least) is in play. Marcel is hiding two things (possibly just one, if true the "one" will serve the purpose of the other object needed as well): so far, something that can track the witches use of magic but possibly even more: their movements, the amount of power used, hints at the types of spells cast, where, when, why, and how...who knows as of yet; and I'm fairly certin he also has an ace against Klaus as well from the well known like a white-oak stake (or similar) or something magical (which could relate to the same object that tracks the witches or something even more bizarre like a "Gilbert ring" that works WITH supernatural creatures, that he has on--if you notice Marcel has A LOT of jewelery...).
I'll add more about your main points when I think them over in a bit...