This is the first of your videos that I check out, and hopefully I will do so more from now on. I quite liked the cozy vibe you give off during the video so thank you for sharing it here.
As for the video itself, I have to strongly agree with Marco Polo on the notion that your video reminds me quite a bit of the theory he mentions, which was basically a haki version of green lantern (without the accessories). I have to be honest though, as far as black weapons go, I think it's mostly (if not downright completely) limited to swords.
It's not so much that the application is somehow limited to swords as a process. It's more so the case cause of the way swords are treated, especially in Wano. It's been heavily hinted that black weapons have an ego / personality and I think that comes from an alternative version of "inherited will", which I heavily attribute to haoshoku haki. By the way, this is why Zoro awakening his haoshoku at Wano was huge for me since it's the same arc where we get to know about the Kokuto and it's hinted that Zoro will make one. Anyway, to grow a personality, I think the fact that most accomplished samurai / swordsmen treat swords as their partners and not as mere tools. They even go as far as to hold burial ceremonies when they break / rust / etc. That's not necessarily limited to swords of course but I haven't seen a hammer user of archer being this passionate about their weapons. Swordsmen seem to be the most "passionate" and devoted to their skills, akin to an artist seeking higher levels of mastery. This is the reason why I don't think even haki powerhouses like Shanks has a black weapon.
It comes down to putting the horse before the cart. You need to be a swordsman (archer / etc) before you are a haki user. That's why we see Zoro polishing mainly his swordsmanship (even during the timeskip) and his haki only as a secondary ability to highlight his swordsmanship.
whawkins90 I do want to point out though, the concept of a "black ship" is actually one I love. The way the strawhats treats the thousand Sunny is like they'd treat any of their nakama and exactly the way swordsmen treat their swords. It's limited in the sense that the crew doesn't directly affect the ship with their haki but it's a fun idea for sure! Maybe what Franky calls "becoming his dream ship" is ultimately similar to it becoming a black ship and perhaps that was the case for the Oro Jackson too.
Sorry for the long reply, really liked that the whole video revolves around you keeping an open mind to the subject. I have to say, I'd love to see a passionate archer / gunner / sniper who treats their weapon like Zoro does his swords. It'd be cool to see a black bow / gun / sniper rifle / etc which doesn't even need bullets and can simply shoot out condenses haki. It'd at least save Oda the trouble of showing the snipers reloading in the future one on one high level sniper fights. : (true though).
Good assumptions, cool presentation, great video overal. Thank you again for sharing it, looking forward to more of your content in the future.
Side note: I know it's not the delinquent you had in mind but Barto fits the bill the most out of all One Piece characters I think. Plus Duval in a deliquent biker gang way.