I think you're right - it does sound a bit odd.
I'd say
He has been the Visiting Professor . . since 2000 or
Since 2000 he has been teaching as Visiting Professor.
In the first example the verb is BE, and so I'd use the simple form. In the second example the verb is TEACH and I use the continuous form to focus on the duration of the verb.
It's a bit of a complicated area - very often I just use my ear, as you have done. If it sounds wrong, it probably is
Anyone else have any ideas?