Been watching this thread, interested if this resistor theory will work.
I don’t think you can get the coil weak enough to make a big difference in the sound without the coil being so weak it can’t draw the plunger up from rest.
That made me think that in addition to weakening the coil, I would shim the plungers to have a lot less travel, and that made me think that alone might do what you are trying.
Have you tried just shimming the plunger to only have like 1/2” of travel?
That alone might work.