I also have a strong preference for not adopting the term 'expert'.

In the strictest sense, I understand we should reasonably be able to apply the broad definition of expert to a practitioner with advanced standing.  However, in practice, the term feels oddly inappropriate to me.

To be an expert is a subjective position and there are many amateur experts (I think Milly referred to this in her post.)
Expert legal/medical professionals (to borrow examples from this & another thread) can only be referred to as such on the basis of their qualifications, profession accreditation and/or specialist skills (which is why I think those terms are more suitable).  

I believe you can still have a specialism (or not) but view this as a separate point to being a meta specialist.  

I am a native English speaker so possibly there are nuances for those with other language backgrounds that I am not considering...