Sixpence
Brownlow Medallist
I believe Y0 is on the Dragon Engine as well, so it'd just leave Y5, but I think that holds up well enough that it doesn't need a Kiwami version.K2, 6 and Gaiden is exactly what it would be like as it's the current engine. This is where I think the optimism from fans is coming from because lots of the required assets are already current and ready to go for both K3 and a K4. So if they made those Kiwamis you would have 2, 3, 4, 6, Gaiden, LAD and IW on the same engine with 5, 0 and 1 on the other and the entire series is a lot more consolidated and approachable for new fans on modern systems.
Dragon Engine
The Dragon Engine is the primary engine used by Ryu Ga Gotoku Studios in the development of Yakuza 6, Yakuza Kiwami 2, Judgment, Yakuza: Like a Dragon, Lost Judgment, Like a Dragon Gaiden: The Man Who Erased His Name, Like A Dragon: Infinite Wealth, and Like a Dragon: Pirate Yakuza in Hawaii...yakuza.fandom.com