Nice work!
The reason the wheel is a 3-cross on the Dyno side is the hub is a little stronger there due to the larger diameter. Since torque is transmitted through the body of the hub, the crossed spokes are there to make things stronger- the concern is failure of the hub body. That's why its a 4-cross on the drive side and that is also why the unit mounts on a 40-hole rim instead of 36. Its all about durability. Sure- the American 3-speeds usually ran 36 hole but they were thinking about it a different way- more as a toy and less as something that was meant to endure for half a century or more.
In practice you can have almost any pattern you want on the non-drive side. I have a radial pattern on my 4-speed on the Dyno side. But on the drive side its a 4-cross.
The 4-speed in this configuration (Dynohub) is rather rare. If you want to talk about something finicky and arcane that's the one...