After some consideration, I realized there's actually a way to simplify the threading. The original method was too clumsy.
Wind all the hundreds of threads onto spool-shaped bobbins.
The threads pass through the heddle grid, then go through a serrated horizontal wooden stick in front. For example, every five threads share a serration, and then connect to bobbins further ahead, each placed on a vertical cylinder.
This makes the process of letting out the thread a lot easier.
With a firm pull, the bobbin turns, releasing the thread.
To straighten the thread, the serrated wooden bar should be made wider, allowing the thread from the bobbin to wind around it once. It has a spindle but is quite tight, requiring force to turn.
To make threading more convenient, a wheel can be attached to the crossbar, connected with a link to a pedal. Step on the pedal, and it rotates half a turn.
If it's heavy and shaped like a wide plank, it tends to stay vertical, making it hard to pull.
