A very interesting area as (excluding the issues of the girdle of the Kohanim and especially Kohen HaGadol,) the other area I know of that discusses a possible permissive use of wool/linen mix is of course tzitzit.

And many people mix up shatnez (wool and linen specifically according to what I was taught,) and kilayim (eg. the mixing of different animals, seeds and fabric types like wool and cotton!)

I’m not discounting traditions here, but the more things we can do to make chidush ha’mitzva in my opinion the better!

Amir
Paimio, Finland