I Think pick six's value isn't in its increased chance at getting sheed. Its in its chance to get one of Aish, Kelly, Scharenberg or billings. I think its a legit possibility that one of those will be available at 6.
To me the most likely to slide is billings. Apparently GWS are keen on Kelly.
Only way i would trade 6 would be if it was to enable us to get 2 high picks eg. Coll 10,11.
That way we could get two of Acres, Sheed, Freeman, Bontempelli, Lennon (or somebody even more highly rated if they slide) who all satisfy needs for me imo.