I don't think any member of the elite GB can be disfellowshipped while in the office, I think they need to be removed first from being part of the elite ruling class CEOs and then latter be DF'd if the need be. I'm of this opinion from what happened to Raymond Franz, Chitty, and Greeenlees.
Ray, was not DF'd for apostacy while on the GB, he was first removed from office given a $10,000 severance package and booted out of Bethel, latter he was seen eating with a member that left the clutches of the organization to which the WT corporation put into effect that eating a meal with a df'd or disassociated member is in itself a df'n offence.
I think the Watchtower will be very reluctant to DF any former GB member because they can do so much damage if they go public like Ray Franz did.