That's only a good idea if they are going to be in constant contact with other wardens. In practice, the North American wardens have months to years where they rarely see one another. They have plenty of time to train in methods to avoid detection and recruit followers. Harry sees more major magical action than any other warden besides Morgan and they still think he had the free time to build his plot for world domination.

And yes, I can see that plot:

Get raised as a warlock by Justin, rebel and kill him in "self-defense".
Bob, otherwise known as the Word of Kemmler.
Take advantage of your grandfather's mercy and get trained further. Earn the trust of several Senior Council members.
Work with local law enforcement and organized crime to build contacts.
Form an alliance with the White Court and later the Winter Court.
Help overthrow the power structure of the White Court while forging "relations" with the new leaders.
Stop the heirs of Kemmler. You're not ready to advance your plans and it'll build more favor with the Senior Council.
Go to war with the Red Court with the support of the Council, Winter and the White Court emerging victorious as the new Winter Knight.
Take down the Formor and openly marry the Queen of the White Court.

Out of context it all holds together but it leaves out some things that don't add up to evil incarnate rising:

Stopping the Denarians at multiple points while resisting their efforts to recruit you, including actual coin possession.
Having KotC show up to aid rather than oppose you on multiple occasions and being ally, mentor, houseguest, baby-sitter (Molly) and drinking buddy with each of the KotC that served since you've been a wizard.
Getting Soulfire from an Archangel.
Actually, telling the Council about most of these things openly with the exceptions of Bob, the Coin and Soulfire.

It's easier to just jump to a general conclusion and summary judgement than put in the work of investigating. Just approaching Michael and asking him to address some areas of concern would get most of this. Unless they think Harry has convinced a KotC to lie for him.

Part pf Harry's problem with the WC is an Image issue. From the average WV members perspective Harry only shows up to meetings that are generally about bad news.
Harry is a young wizard who should be kissing the rings of older members, trying to make friends and networking. Instead he shows up to meetings late, in the wrong attire and with the attitude that the Council is beneath him. Harry shows up on the WC worst days delivering bad news and expects the WC to back him up.
Image Harry as a core worker, Dude got the job based on friendship  with the manager, skips meetings, shows up to criticize the work you have done, claims he can do better than you idiots.

Goes away for who knows how long. Breaks the rules ,is saved by senior management , wants your help with a project he messed up, and you are ordered to help him. Dude f***s off to who knows where.  Comes back barely contributes. And then when the project seems like its doomed to fail, shows up with a brilliant solution and gets all the credit. That's Harry from the Average WC member

All anyone knows about Harry is that he is trouble. Harry makes the barest amount of effort to make friends with members of the WC

I'm sure Luccio used just that argument with Harry's enemies on the Council.  There's precedent, too.  The Council tends to make people with warlock-ish talents into Wardens so they can watch each other.

IIRC, JB said once that one of the reasons Chandler was a Warden was precisely that he had a knack for time magic.  As a Warden he can use that knack to police the magical world, and at the same time the other Wardens are around him all the time so if he starts to misuse it, he can be detected and dealt with.  JB also pointed out that Molly might well end up as a Warden because of her mind magic talent.

Making people with warlock tendencies warden actually makes sense in a way.
1) it reminds what would happen to them if they went warlock ie caught and beheaded 2) it shows them the harm abusing their powers would cause. They mostly end up hating warlocks and everything about warlock ensuring they dont become warlocks.

Agreed, though I think the Merlin was right in the case of the Koren Kid, he was too far down the tubes to rehab with the Doom. I do think Harry was also right when he argued in Molly's defense, that most of these kids deserve a chance at rehab.  The problem Harry will run into will be the same problem that the Merlin and the White Council have run into, enough qualified wizards willing to take on the risk of being responsible for an apprentice under the Doom, since they themselves would suffer the same fate if the apprentice went full warlock.  And yes, I think Harry capable of executing a full warlock kid.  Harry may find himself having to reform the system so that it is fair to kids who do dumb dangerous stuff with their new found talent before they know better, and at the same time weeding out those who cannot be redeemed... Easier said than done...

Agreed it easier said than done.
Even without the doom over their heads( I doubt Harry would retain it of wizards willing to rehab young kids who are potential warlocks) he would still have difficulty finding wizards willing to play babysitter for a potential warlock. Dark magic is addictive. Helping someone kick an addiction is hard and most people ain't suited for the job even if willing which most people aren't.

I think it was Summer knights. He laughed at Harry's bad latin ( stupid correspondence lessons)

Been thinking given their rapid rise in rank and the fact that they seem to be trusted by the Establishment. Who are Carlos and Chandler's mentors.
Is there any Woj about them?
Cause i think there is so much there!.

Chandler is a wizard Luccio trusts above most. Carlos is Carlos and holds any important position at a young age.

All of that, yes.
I think access to Papa Raith's library is on Mab's agenda (likely, as you suggest, to power-up Harry).
Further isolating Harry from his Mortal allies (Mab sees mortal ties as a weakness, after all).

The biggest one, I suspect, is that Mab wants to find the Whampire Nemfection-vector:  Papa-Raith had Outsider-fueled protections, and an Outsider-fueled curse (that the porn-starlet coven used), and Justine got Nemfected apparently from working closely with Lara.  Something seems to be rotten at the core of the White Court.

And -- oh look! -- Mab has a Starborn WK (just the thing for stomping on Outsiders!); time to toss a HarryDresdenGrenade into that bunker.

Thats a great image. Genuinely laughed.
But that seems like a Mab thing to do.

  Only problem with that is Mab is fighting Outsiders.  So why would she sacrifice Harry to have him come back possessed by an Outsider?

Ah that the catch. Magic always has a price.
A starborn is sacrificed to keep the outsiders out but in exchange he/ she brings something back with him.
Plus dolist reason it would mess Harry up. Jim is that much of a bastard to do it