It's the easiest to make. Most of the cast is japanese so they only have to get a forign actor for Joseph, it's not too connected to the other parts, and in comparison to other parts it's fights are far less over the top and easier to translate into live action.

Koichi is typically 5'2 but Araki draws him smaller. Here he's 5'5.
Close enough. Also all the characters look like super models which is honestly pretty accurate.