And dont undersell what top tier means, luffy right now is on the cusp of it. If it was that easy, there would be a lot more top tiers runing around mate.
And how many other characters have both Future sight and penetration CoA?
Im not saying penetrative haki is basic in itself im saying luffy learned the basics of it as he only had 3 days.
He was trying to learn it for nearly 2 weeks. There is no "basic" penetration haki. That implies that there is advanced penetration haki, but we've never seen such a thing. The only other example we've seen of penetration haki is what Rayleigh did, but we know that Luffy can do that.
After that he could fight a top tier 1vs1 and cement his position before fighting Blackbeard.
why do you think he'll cement his position after wano when
- he was already called an emperor before wano
- he already has a 1.5 bil bounty
- his strongest subordinates(Zoro, Sanji, Jinbe) are at the bare minimum low YC level
Wano is the most hyped arc in the post skip period. I don't know why Oda would cement Luffy as a top tier after wano.
Oda also had moriah and blackbeard happen for a reason, the marines questioning wano and its ties with so many big players for a reason, Shanks( this one is a stretch) wanting to talk about a certain pirate( Rocks or blackbeard, either way ties to wano) for a reason, warlords( mostly hancock and weevil have a reason to end up in wano after the disbanding), and then the whitebeard remnants are coming in too by the way. Oda wouldnt do all of that if he believed luffy can solo a yonko at this very moment. He said himself that this would make marineford look cute, and the hints are there. Mark my words.
Blackbeard and Moria could honestly show up at the end of the war, after the Rocks alliance is defeated, to kill Kaido and steal his DF
The warlords straight up won't come to wano. Maybe weevil will, but if he does he will be an antagonist(due to Bakkin's connection with Rox), not an ally. Oda said that Hancock will be in trouble, which implies that the marines will most likely capture her. Anyways she will be too busy fighting the marines invading Amazon lily to do anything in wano.
As for Marco and the rest of the alliance, they could just be meant for big mom. That's the thing I'm getting at, if you assume that Luffy can't deal with Kaido by himself(for the most part), then you also have to assume that Big Mom is defeated by plot induced stupidity, which would ruin all the build up for Rocks 2.0.
If we were facing just Kaido and Kaido alone, then I would agree with you. Oda wouldn't put together such a force, if Kaido was meant to be 1v1ed, but when you put big mom into the mix, it makes sense. The only way big mom can be satisfyingly defeated is if Kaido is mostly dealt by with Luffy and the rest of the alliance deals with big mom.