Hi,
I implemented this kind of solution in my hand-made yoke described above.
With this solution, the trim is purely hardware so the trim position doesn’t have to be communicated to the sim. For the sim, it just stays in neutral position. And there is nothing particular to do with the Y position.
In my case, it was originally designed for a physical cockpit, and the actual trim position was displayed on a mini-oled screen integrated in the trim-wheel. So the information about the trim position used to stay “inside” the yoke controller (Arduino-based).
Then I switched to VR, so the visual feedback had to become available in the sim as well. Which means transmitting the trim position so the trim indicator is updated in the virtual cockpit. BUT in this case the effect on the attitude has to be canceled! This is highly important of course, otherwise the whole thing becomes incoherent. Which I explained in detail in this thread.
Hope this helps (sorry if not, I must admit that your post was a bit long and didn’t have time to read everything 
)