Looking back at your earlier posts, I see that you drilled 3/8” holes in the staves’ feet. That seems big enough to hold a threaded insert (which specific size, I’m not sure). Then you can run bolts up through the base into the inserts. I’d want clamp scraps on either side of the stave feet to make sure they didn’t split as the insert went in.

Doing that doesn’t eliminate the short section of tubing from the base to the lower intersection of the three staves. Could you add another recess for a hidden nut at the bottom of the intersection point? Then your brass tube would be secured  by nuts on both side. The lower nut would be in the staves instead of inside the base,

If that could work, you just need a way to rub the wiring to the lower pipe opening. I wonder if you can buy a hollow nipple small enough to act as a bolt for the stave closest to your driver. That would give you a wiring path from the driver into the foot of the stave. Then you could cut a channel on the underside of that stave to hide the wire. You could secure the wire with hot glue so it’s not permanently attached.

I don’t know if that would work. Even if it did, it would require significant effort (and risk to the staves you carefully shaped). It would also require a round plug for the hole in the center of the base, but it would be in the shadow from the legs, and I doubt anyone would see it.

If it were me, I’d probably just leave it as-is. The original light has a tube there too. If you ever build another one, you could consider a design that eliminates the bottom post.