Any question answered...

I'd say you're missing the parts in 1, 2 and 3. But yes, the freehub bearings run on the black axle.

Or more importantly if I put a solid spline in there I could make a beater fixie skidder disc out of one of the worlds most expensive disc wheels...

You'd need some way of constraining the DS of the axle, and preloading the bearings, and attaching the fixed cog to the axle. But yes, looks pretty doable with a bit of machining. If you were really keen you could machine a piece which fits in the splined section in the hub and allows you to attach a fixed cog through your locating system of choice, whether threads, bolts or magnets. I'd advise against magnets...

Or more importantly if I put a solid spline in there I could make a beater fixie skidder disc out of one of the worlds most expensive disc wheels...

the toothed ring is threaded into the hub body, so no.... unfortunately

if I put a solid spline in there I could make a beater fixie skidder disc out of one of the worlds most expensive disc wheels.

As everybody else has already said, the drive goes through a thread which you can't lock in any practical way, so skids will just unwind everything. The easiest way to attach a fixed sprocket to it in order to make a suicide hub would be to take out the splined part and make the mounting thread on your fixie adapter to match the female thread in the hub shell. Loctite the adapter properly into the hub shell and use a threaded sprocket with no lock ring, so that if anything does unwind it's the sprocket off the adapter, not the adapter out of the hub shell.