For me, that would still be a high action, though I expect it might come down a bit with lower nut slots.

If the top stays as it is but just the neck bends, then that should be able to be straightened out by the truss rod. If the top is pulling up, then you need to do something to stop that.

Your idea is certainly working along the right lines, though I'm not quite sure just how you could tension the wires. I think the tips of your triangles, if made of wood, are going to be fairly weak and may be prone to breaking.

You may be able to rig up a Strat-style trem claw arrangement, with the wire attached to the claw and you can screw that into the neck black and adjust the tension via the screw, but even so, the practical access for screwdrivers and drills in the soundhole isn't easy. Looks OK in theory, but you can't grip things well once they are inside the guitar.

There is also the distinct possibility that the tension wires will vibrate and be audible when you play.

What about making a Bridge Doctor type wood block, but with a metal threaded insert and use a length of say M6 threaded rod (instead of the plastic rod and metal screw)? You could either slot the soundhole end of the rod so you can screw it against the rear block, or maybe glue/solder/weld a nut on the rod, so you can turn it with a spanner/socket wrench.