Those aren’t the precise words I would have used, but I as I understand them, they convey the substance of what I mean.
I see RCs often arguing that the Catholic church is the inheritor of Divine promises of preservation, and the instrument and steward of Holy Writ, and that Rome is the only church with historical descent, and thus all are to submit to her. While you want to argue that the magisterium is necessary, and why, is not the above your basic argument as to Rome being that magisterium?
After this we can continue.
I don’t think it is helpful or entirely accurate to talk in terms of “submitting” to Rome. The ministry of the bishops of Rome is a ministry of service. It is certainly not about domination or glorification for their own sake. Still, we do believe the papacy should be honored, in the same way that a master’s servant should be honored because he represents the master.
There are many authentic local churches of apostolic descent, but their communion with the single true Church established by Jesus is imperfect if they are not in full communion with the church headed by the successor of Peter, who uniquely received from Jesus promises relating to authority and was entrusted with unique tasks, not least of which are to “shepherd the sheep” and to “strengthen the brethren”.