There is no organizational structure above the local churches. The one who is functioning as an apostle in an area will be the one that appoints the elders in the churches under his ministry. His ministry of the truth and spiritual leadership should also help the churches to grow and to keep on the right track but otherwise he does not control any of the affairs of the local churches. If an apostle becomes the one that is going off track then the churches will find that his ministry is not as helpful as before. There does not need to be any organizational procedure to deal with him because he wasn't in any kind of organizational position. It is simply that his leadership is no longer valued and respected by the churches.
In all these matters we seek to follow not just the teachings but also the patterns in the New Testament. There is no record that Paul directed any of the local affairs of a local church even though he exercised very much to help them spiritually. For instance, when all the saints in Asia turned away from Paul (2 Tim. 1:15) he had no organizational structure in place to try to bring them back into line. That would have brought his ministry into the realm of human politics. So also it is among us. If the saints and the elders in a local church want to distance themselves from the other churches then there is no organizational structure to stop them. Whatever tangible assets they have, like a meeting hall, are theirs alone.
Actually, the strongest tie among the churches is the mutual fellowship of life. To some extent each local church is different because the needs of the saints and the capacities of the leading brothers and sisters are also different. We care for spiritual unity, not outward uniformity. But if a church is going on well then other churches will naturally learn from it and seek to apply the same principles to their own situations. Just as the members of the body should be mutually adjusted by being blent together (1 Cor. 12:24), so also the churches are blent together by the fellowship among them.
You might be thinking that all this sounds too unstructured to ever work or to provide adequate protection against corruption but our experience is the opposite. When there is no organizational hierarchy then there is little opportunity for political corruption. The more all the saints, especially the elders and the workers, know how to interpret the anointing of the Spirit in their spirits, the better it works. We expect that the human leadership in and among the churches would simply be a channel for the Lord to be the real Leader.