Best way to put microphone on
I always see microphones attached directly to the violin. Yea, there are microphones like DPA 4099v which still gives better sound. Still, I'm wondering why not attaching somewhere on our heads, or ears? Considering we're not moving our head so much and actually that's not so correct to move head a lot, so why not stick it somewhere there?) Anyway, I don't think whatever's in our head, whether it's earrings, necklace, eyeglasses etc. would affect to the violin sound much as something additional installed to the instrument itself. Did you try something like that? I still have no microphone to get any chance hahaha) But that's still important thing in my opinion.
Once i saw a violinist do exactly what you describe: he weared one of those headphone microohone for talking or singing, but the capsule was extended in order to pick the violin's strings from above.
Some players keep their heads rather still while playing. Leonid Kogan for example. Others bob their heads all over the place. Phillipe Quint or Nigel Kennedy, for instance.
I attended a concert two weeks ago where the violinist (Catherine Fraser) clipped her microphone on her right collar, and covered it with her hair. She did this on stage.
It means that's not necessary to attach mic to violin, good to know that) now, the main task is to choose the proper mic for violin hahaha
The best way to record a violin is to have a condenser microphone mounted on a tall stand, in the direction of the scroll, looking down into the tailpiece from a couple of feet away.
Clipping to the collar is a good idea ... collars don't move a lot when you turn your head. But that's the kind of thing you'd need to practice and optimize. And probably wear the same kind of shirt every time.
I've seen a hanging microphone used for amplification in a hall before.
"Cotton" you need to design a helmet that a violinist can wear that will position a Telefunken U-47 directly above their violin all the time.