So what stops the inheritance being done through haki means? Nothing what so ever if oda wants it to be .
The way i read luffy vs kaido comes from multiple moments in the series. Doesn't mean you have to agree with all this but anyways.
1. Chapter 597- The only way luffy coc haki gets stronger is for the user to get stronger. Luffy awakening his df made him stronger overall so his Coc gets a buff.
2. Chapter 778-even though this was before coc coating i still think this is true the person with the greater haki wins. this is the determining factor for who wins the clash who haki is superior
3.chapter 1037- the only time kaido haki was shown to get stronger haki is when he is drunk to which he overpowered luffy to me this solidifies drunk kaido haki>sober kaido haki at least, and again the one with the spuerior haki wins the clash.
4.In the final clash luffy haki surpassed kaido haki just like oda depicted in chapter 1037 they met in the middle at a even clash. Between the moment of kaido asking what world luffy would create and luffy telling him his haki surpassed kaido and he won the clash sending kaido all the way down into the volcano.
5.This last part is nuanced but i do think it matters as well. In chapter 597 Rayleigh tells us to never doubt that is strength, and yet in chapter 1049 we see kaido go into a flashback mid clash where at the end of it he says If he is the same as the man you're waiting for,king... then i think i know who joyboy is to which king responds with apprently odens desire to open the country is meant to welcome joyboy this to me is kaido starting to doubt himself and right after that he questions luffy to which he is defeated.
I do not think the fight between them was simply won due to physical strength of luffy awakening. Ultimately when it comes to a haki clash in the end oda always goes back to whose haki is superior especially when it comes to luffy.
Because haki only has 3 colors. Odas not going to retcon the entire haki system just to include the Will of D. When it’ll be easier just to have it be a different ability and the “Will” is just a figure of speech like Sabo inheriting Aces will through his fruit.
And your points about the Kaido fight don’t make a lot of sense because you’re taking out of context quotes instead of just looking at the fight especially when the quotes don’t relate to what you’re referring to:
1. Luffy awakening his df doesn’t make his base form stronger. It gives Luffy a stronger form, but his haki remains the same throughout the forms. Otherwise Oda would’ve specifically stated it grew stronger just like Oda did for Kaido.
2. This quote is about a swordsman being able to slash through haki. If the opponents haki is much stronger it blocks the sword then yes the haki decides the match. But this doesn’t really affect Luffys fights cause he’s not a swordsman?
3. Yeah Drunk Kaidos haki > Luffys haki, yet Luffy won that final clash because of Bajrang Guns physical strength was much stronger than Kaido could handle.
4. Luffys haki never surpassed Kaido, Kaidos haki was always superior, however, Luffys physical strength let him overcome the difference and land the final hit on Kaido
Kaido lost because Luffy became Joyboy, literally, because of Gear 5 as even Kaido said that’s who’d defeat him. The haki helped him, but that wasn’t what gave him the win. Never was.
Even now, we see examples of characters with weaker haki beating those with stronger haki. It’s a common occurrence in the manga