Yes, exactly like that -- and Roman Concrete and Stradavarian Violins. 

Peabody set the spiders to watch the Way from Chicago to Scotland, not Mab. He's been wary of Dresden, since he was one of the few Wardens that Peabody couldn't influence.  They showed up to assist on the Island as well.  Even assuming the spiders are somehow associated with Winter, Mab was having quite a few rebel issues until Cold Days cleared that right up. 

I think Peadbody and Rashid know different Ways to the Island as evidenced that they arrived at different Island locations.  Keep in mind, that the Ways work as travel short cuts because different spots near each other in the Real World can be very far apart in the Never Never and vis versa. I don't think it's like a bus route where you get off at your stop.   

As for what is on the Other Side of the Island, I suspect it is the realm of Hades -- not the vault, but the prison.  Hades made it pretty clear how very similar Hades is to Dresden -- down to pet preferences. 

I'm not sure that I buy a loss of institutional knowledge in the White Council -- at least in terms of the way it operates.  After all, Langtry, Listens to Wind and McCoy were kids during the French and Indian War / Seven Years War (1756) and have had birthdays in four separate centuries.  Ancient Mai is even older still.  Rashid might be the oldest human, given that he lives in a time dilated parallel dimension near the Outer Gates.  I'm pretty sure I read a WoJ that he ran around with Muhammad. 

In Wizard terms, the Fall of Constantinople is only two Wizard generations ago; Charlemagne four generations; Julius Caesar is only seven. 

Given Wizard secrecy, it's easy to see them losing "tech" that was held as individual trade secrets, but not losing public customs. 

That being said, I do suspect that the Warden was once the head of the White Council's police force, aka "The Wardens." 

I would like to point out that Strife and Division are not necessarily bad things -- in other contexts, we refer to them as competition.  Unity for its own sake is not actually that useful and often leads to stagnation.  Winter is very much a improve through struggle kind of place. 

My point is that Mab would certainly be interested in little healthy competition between her servitors in a general sense.  Moreover, someone like that might be useful if used in the correct circumstances.  Therefore, ...

She sends the Nameless Son to Marcone after Proven Guilty (behind the scenes) -- let's say during the events of White Night where by pure coincidence (I'm sure) Marcone joins the Accords and Ms. Demeter executes her plot to betray Marcone to the Denarians and Lara Raith (now virtually a Winter Vassal) secures her hold on the White Court of Vampires. 

I wonder whether Marcone was actually Mab's back-up Winter Knight and not Thomas. 

I think the intent in Turncoat was for Peabody to become Warden (he is an expert on summoning and binding, his book on Erl indicates that) but to do that he needed the current absentee Warden Dead, and if that was Fortier it explains why Peabody aimed the Captain at him for an otherwise motiveless killing. Unfortunately Harry by pure fluke beat him to it. The Murder and Harry acquiring the wardenship happen in the same book, coincidence, perhaps, but Battle Ground showed Christos was not the stalking horse he was portrayed to be earlier destroying that weak motive, and it would depend on his election succeeding. Killing the Warden means the wardenship is up for grabs definitely unless some idiot just happens to blunder in.

I completely agree that LaFortier was very likely the previous Warden.  McCoy and Harry thought the murder of LaFortier was to drive a wedge into the White Council and get one of the Black Council on the Senior Council.  This honestly never made any sense at all. Why would the Black Council need a seat on the Senior Council when they had Peabody "taking care" of everything?  In reality, the Black Council was very effectively controlling and influencing the Senior Council already.  Frankly, this is more of Harry and McCoy thinking everything is about Wizards. 

Additionally, Wizard Christos doesn't seem that bad -- just a self-important blow-hard (like all Wizards).  He doesn't seem to be particularly anti-Dresden either.  Moreover, he was seriously wounded -- very badly burned -- during the Battle of Chicago and was conveniently absent from the vote against Harry.  Indeed, it seems likely that the only Senior Council members present were Merlin and Mai (and maybe Liberty) -- Christos, Listens to Wind and McCoy were all hospitalized.  Sure, he went ape-sh*t on Harry during the Arianna incident, but let's be honest -- Harry deserved every bit of that and more. 

It is also clear from Turn Coat that Peabody and Rashid knew of Ways to Demonreach.  However, they are clearly different Ways.  Rashid came to the Docks and did not set foot on the island, whereas Peabody came to a different part of the island.  Even if a Way from Arctis Tor exists to Demonreach, and Rashid used that, Peabody's way is not the same.  Maeve, Lilly and Fix used hang-gliders to get to the top of the island.  Binder and the White Court vampire used jet skis. 

I also believe that a Way made on Demonreach would go to Hades, it would not go to the vaults, however, but the prison part of Hades.  This is why Harry couldn't open a Way on Demonreach and get to where Nicodemus wanted to go.  Hades is probably quite large. 

Finally, while Rashid probably has max respect from Mab, I doubt she let's anyone know her secrets. 

My reading of the end of Battleground is that Harry and Lara (and Molly) agreed to the marriage and the year's wait simply as a means of buying time.

I can easily envision a scenario where Harry and/or Lara object given the inability of safely consumating the marriage.  I wonder then if Mab will intervene by making it so that Lara and Harry can have "normal relations." 

After all, the Leansidhe was able to quell Susan's hunger and Mother Winter offered Harry an "unravelling," that could have cleansed Susan.  Since the White's "parasite," seems to be more separate from the host than the Red's "hunger," I imagine it might be easier for Mab to quell it situationally. 

Sounds more like a Rick and Morty bit to me.

Been awhile since I checked in on this, but there are some interesting points.

(1)  LaFortier as the most recent Warden.

I really like this idea as it solves -- at least in my mind -- some nagging issues from Turn Coat.  To what's been stated above, let me add one tiny additional assumption.  Assume for the sake of argument that the existence and nature of "The Warden" is restricted information known only to the Senior Council members (and maybe not even them).  There is some support from Rashid on this.

First, splitting the White Council into factions is simply not the same kind of stakes that earlier and later books establish.  While no law requires every Dresden File to have all creation as the stakes, a possible fracturing of the White Council is just not that significant.  Sure, the Wizards think that they are super important and that the Senior Council is the most important of all; however, in reality they are just one player in the Great Game and a fairly downscale retail outfit when compared to Heaven, Hell, Winter, Summer and even some of the more scuffed powers like the Fomor, Asgard and Hades. 

If the White Council split, would it really matter that much?  Harry and McCoy seem to think so, but I doubt that this is really true. 

Second, if splitting the White Council is the goal, why not kill the Merlin instead?  If you wanna see some infighting and jockeying for power, just wait for that guy to ride the Night-train to the Big Adios.  Why not Mai? She seems less capable of defending herself in a physical confrontation than LaFortier.  If you can program Lucio to kill La Fortier, you can program her to attack anyone. 

Third, Christos has been a disappointment as a Black Council suspect.  Harry and McCoy were initially convinced that he was, but in the subsequent years, I haven't seen any real evidence that he's actually bad -- he's just a self-important jackass (like all the others).  Indeed, I don't think we have any real evidence that he's actually anti-Harry.  Crucially, his injuries (badly burned) likely prevented him from voting on expelling Dresden.  (I think only Merlin, Mai and maybe Liberty cast votes).

Given this, just opening a Senior Council seat seems like it doesn't quite fit.  On the other hand, given ALL of the subsequent events, clearing a Warden out of Demonreach and then trying very hard to get rid of the "accidental" replacement or suborn him makes sense.  It also makes sense that the Senior Council didn't immediately appoint a successor (assuming they can) and didn't check up on the place.  They are so self-centered they assumed that the LaFortier Affair was about his Council Seat and not his Night Job.  No one but the Senior Council knew that LaFortier was the Warden, after all, at least in their minds. 

(2) Harry did not "stumble" on the Job

I don't think Harry accidentally stumbled on to the Job as Warden.  He was carefully stage-managed into the job by none other than Uriel.  In fact, recall that Harry could not have been the Warden without Soulfire.  I'm sure an older, more skilled wizard could have managed without Soulfire, Soulfire was just Harry's cheat code to getting that Job a hundred years too young.

(3)  Harry is the Adult, not the Toddler

While I like the toddler with a gun metaphor, in this metaphor Demonreach is the toddler, not Harry.  Demonreach is sort of a super-natural Bam-Bam from the Flintstone's cartoon.  Harry is the adult, because his threat assessment and response software is more calibrated.