I see no reason to entrust the primates with that kind of gatekeeper authority. The very idea rests on the outdated notion that the church is a flock, of which bishops are shepherds. This notion apparently derives from patristic times: Before leaving for Jerusalem, Paul reportedly exhorted the elders of the church of Ephesus to keep watch over "the flock of which the Holy Spirit has made you overseers," and to "[b]e shepherds of the church of God" (Acts 20.28). Perhaps taking their cue from Paul, some early church leaders wrote in a similar vein, notably Ignatius. All this presupposes that the rest of us are sheep who must be led by their wise, benevolent human overseers. Nonsense. Bishops are not divinely-appointed monarchs; they're "hired help," with specific jobs to do.It is to laugh. Anyone who has ever watched a mainline church in the throes of controversy knows that bishops are not the leaders one looks to for theological restraint. Controversial votes in the ECUSA General Convention are decided by the deputies; the House of Bishops is always comfortably in the vanguard.
Those who hold the croziers for the dioceses of ECUSA lack almost any accountability to anyone. Hired help? They're more like "presidents for life". When it comes to shepherding, they are as wont to drive their flocks into new fields as they are to keep them within bounds.
And not to put too fine a point on it, but the language of liberals is all too often exactly expressive of the opinion that the laity are dumb sheep who need to be led to the green fields of tolerance and every other liberal virtue, and that without this direction, they would stray into choking down the thorns of bigotry. I have yet to find time to read the material about the proposed convenant, but it's rather obvious that the biggest problem with letting the primates at it is that the liberals would be consistently outvoted.