I'm not really a fan of adding the Kingpin to the MCU. I think the Kingpin worked very well in the Daredevil series, but I don't consider Donofrio's version a physical threat for Tom Holland's Spider-Man. A physical confrontation wouldn't make sense anyways, and a kid battling an underground crime organization doesn't really seem to be what the MCU is missing. I like the idea that the Kingpin is able to take advantage of the wreckage that the Avengers leave behind in their wake and I'm almost hoping for a similar situation after the events of Infinity War. With Spider-Man being positioned to take on a more significant role in a potential "Avenger's 2.0" lineup, I think it makes sense to continue to have Spider-Man take on more significant villains in the standalone series that are a greater threats and leave the Kingpin to square off against the Defenders. I think it's pretty much a given that Venom/Carnage are going to be teased as future Spider-Man/MCU villains anyway. There is too much outerspace content in the MCU to NOT include Venom at this point. I have also always liked the idea of Spider-Man movie with Hobgoblin as the villain, played similarly to Heath Ledger's Joker. The identity of Hobgoblin wasn't revealed initially, and instead you had this character that inflicted chaos just to prove that he could. Hobgoblin could just go running around New York and nobody has a clue who he is. I think that would play very well in the MCU, because Spider-Man is also the only character in the MCU that hides his secret identity - think about it. That could be a very interesting film that explores the conscious choices Peter Parker makes to protect himself.