WT play matters both ways to its benefit. Just as WT often claims clergy privilege in court, the required actions of its representatives do not support those claims which the courts have now started to recognize.
While elders may need to be re-appointed as such when they change congregations, a person who is DF'd in one congregation remains such if they relocate or even visit any other congregation regardless of location.
Actually, WT will sometimes assign an elder(s) from other congregations to a congregation that is experiencing problems. As such, those assigned elders remain such and do not need to be re-appointed.
If the organization was truly organized congregationally, each would choose its own elders without further approval from WT, and each congregation's elder body would be free to make decisions without authorization or fear of penalty from WT.
Congregation elders are not free to make decisions but are mandated to follow the policies and procedures of the WT organization (or other corporate entity ie: CC), thereby acting as that organization's agent. If elders do not do so, they risk censure, removal from their position or being removed from the religion through DF'ing.