@Marti-MG I hope I'm not too late.
If you want to use GPIO18 (PWM_CH0) only then you should remove U6 the 6 pin SOT23 marking C145 SMD IC only.
See also the official Omega-Power-Dock schematic.
After this modification Power Dock 1 remains fully functioning. You can check the battery level visually with the pover-dock command as before - but the 'battery level check' scripts will not work of course. Power Dock Checking the Battery Level
[SOLVED] I found out the servo is discontinued. I think it has flaws in its design. I can't explain why it sort of works (only one direction) from the USB thing and does not from the expansion board, but I got 2 different newer winch servos and they work great in both directions from Onion and my USB thing, so it has to be a faulty servo. I have a feeling it had a 1 to 3 turn limit before breaking a cog if it driven past that, then once the cog is broken the pot doesn't return the right values and its all screwed up. Anyway the expansion board seems pretty bullet proof for noise and EMI EMF, I man handled it pretty good.
here is a basic idea on how i would like it to operate.
I will make the actual models on the weekend. Its basically like your board, the only difference is the daisy chain, and the there is only 1 power input. The omega will receive power from the servo board.
@Douglas-Kryder The MT7688 does have four quite sophisticated hardware PWM units, however only two of them (pwm0, pwm1) have pins exposed on the Omega2. See here for some information , albeit in the context of generating WS281x LED signals.