There is no evidence for such a system of governance in the early Christian community, and certainly not before the emergence of a definitive all encompassing centralized authority that would be invested in the Catholic tradition of the fifth century.
Indeed, ecclesiology, the subject of Church rulership, is only defined in embryonic terms in the NT. Evangelicals believe that the Holy Spirit permitted various forms of congregational [that is, independently constructed congregations with local elders] authority to evolve within the believing community. As churches became established farther away from the original centre of gravity in Jerusalem, these manifested themselves as independent communities whose local body of elders did not interfere in the affairs of other congregations. If such fissures as threatened the existence of the community occured, then the arrangement of Apostles allowed for the settling of disputes.
It appears that the Apostles were the only constituted authority who were permitted to enter various congregations and settle disputes between various localized units. Otherwise the various congregations or churches got along amicably with each other. In fact they depended on each other for survival against an increasingly hostile civil administration.
That these various churches had a measure of autonomy can be seen in the way that Paul and Barnabas were anointed by the local church at Antioch to embark on the First Missionary tour [Acts 13:2] without any pressing need to gain the approval of any so-called GB at Jerusalem. Indeed the repetitive concern shown in this narrative is the leading of the Holy Spirit, whose Presence apparently transcended any human authority.
Also, Paul had sufficient confidence in Titus to permit him to make appointments of elders in his own church, and those churches which were entrusted to him, without the need to have any interference from a remote GB. [Titus 1:5]
The existence of a GB suggests a preoccupation with doctrinal probity and the need to establish what was and what wasn't orthodox. Actually, history shows that the common thread that ran through the first century community of believers was a love for Christ and the worshipping of Him, sometimes in a primitive liturgy, sometimes in pious devotion. Orthodoxy, and the need to define it arose only when various disputes, usually Christalogical, arose from among the believers. Such a requirement would be recognized as necessary only in the mid fourth century.
Whatever the meaning of "Hegemenois" used at Heb 13:17, it is clear that the application is to a localized area and pertains to the immediate geography of the readers. Hence whereas, the writer urges the readers of Hebrews to "be obedient to those who were leaders" among them, he also urged them to convey to those same leaders his best regards. [See verse 24, at the end of the letter] This would be impossible if he had in mind a supra-national body claiming to have exclusive rights to submission on the part of the rank and file.
Thus, the Watchtower structure as it exists today finds no warrant in the genesis of Christianity, but is a development of a much later, hierarchical protocol that developed in the emergence of the Roman Catholic Church. An organization that the Watchtower presumes to despise.