What would be the purpose for that? Threads must be both RH to transmit torque from DS to NDS in forward and both LH thread would be used to transmit torque in the other way (from DS to NDS but braking torque during skids).
Being RH and LH will make sure any way you torque the hub you can't transmit anything if it unscrews.
Turnbuckles are good for clamping without moving the two pieces that are being clamped - Like in a cable tie or applications you mentioned and other cases.
In this application, once tighten (with whatever threading) and epoxyed then the spokes will be like safety-wire keeping the hub from untwisting. I will remove the spokes to do the modification.
If I remember, there was a carbon hub with weird carbon spokes (a sheet of carbon with spoke like pattern either side) that used the hub as a way to tension the spokes by spreading flanges apart. (LE: found them,
Mad Fiber wheels )
Lowering the chainline could be a good thing, but if i make my own modified hub then I can have better support (putting bearings very near to the dropouts), and very good side support from the spokes. And will certainly not run into clearance issues with any chainring in future.
As for connecting. Threads are rarely a good way to ensure concentricity. And hard to thread with a boring bar at that small diameter. Tapping it with normal taps and dies is inconvenient as I don't have such large taps, and the hub shell is 17.2mm on outside.. not enough for M18, too big for M16 (will remove too much material.. will have to measure but i expect the wall to be less than 2mm to work with).
So a pressfit sleeve with some epoxy should do the trick. Also the angled spokes will keep the hub together by a lot of clamping provided by 36 spokes. (axial clamping between flanges i mean)
I'll do some further measuring, and start working by disassembly of spokes. Will do some calculations beforehand (clenching fingers for some CAD/CAE/FEA analysis). Thinking to upgrade the axle and the hub to sealed bearings. For the axle i think I can fit a 12mm axle (and filing two flats to enter the 10mm dropout. Would not like to file on these fine Campagnolo dropouts for my franken-hub). Will be back after some 3d modeling.