I had to gather some courage to bring up 'needle action' again, considering how good it is by now, and me being fully aware the complexities that had to be overcome to get to this.
So, please consider this to be mainly some observation. If you think you've done all that you can (or are willing to do), feel free to ignore this.
Below a comparison between MusicBee (top) and foobar2000 (bottom).
I most certainly prefer the liveliness of your implementation to the RMS approach of the foobar2000 plugin.
And yet, there is a nice calmness and 'authority' to foobar2000's needle action.
And while in comparison it may come across as 'slow', it is actually faster in responding to 'general' loudness increasements.
It's like an older boxer that seems a bit sluggish, but will still throw the first punch.
What I think is what is still making the MB needle a bit nervous, is that the needle is allowed to move many times back and forth in short amounts of time.
If it would be possible to 'dampen' or restrict the allowed frequency of movements within very short time spans, it might make things look less nervous and jumpy.
But I could imagine this can't be done without also affecting the more global rise and fall times of the needle. Which are good as they are and probably shouldn't be touched.
Anyways, I hope you see what I mean and my observations make some sense to you?
Here's the comparison:
