That you seem not to have not thought about the passage very much.
Except that St. Ephraim did not actually make that connection. You are imagining such a connection into the passage by way of petitio principii, namely by assuming that Christ handing the keys to Peter signals his intention to make him into the sole recipient of them and the sole recipient of the office of royal steward (which is that which you had set out to prove in the first place). St. Ephraim connects the steward, like all of the authority figures of the Old Testament, to Christ, but the connection to Peter as the sole inheritor of these keys is simply not explicit. Firstly, St. Ephraim only mentions Peter insofar as he is making a point that Christ could not have given Peter the keys, if Christ himself were not the embodiment of the authority of the Royal Steward, but he does not mention. Secondly, it should be clear from the context that since the keys mentioned are the keys of priesthood and prophecy, that these keys were not passed uniquely to Peter, for all bishops are highpriests, and other Apostles were prophets. Thirdly, your pet theory is at odds with the many Latin fathers who believed that Peter in Matthew 16:18 was accepting the keys on behalf of all of the apostles, all of whom have use of the keys when they bind and loose.
But you did not really satisfy my request. I asked you to find a passage showing that Christ explicitly intended to reestablish the office of royal steward (which as you will notice, this passage does not). I said that a passage making a typological connection would be a good starting point for a discussion, but based on your bizarre bout here of prematurely self-congratulatory pomp, I can only assume sadly that no discussion shall ensue. However, if you are ever looking to cease congratulating yourself and to engage us in dialogue rather than conceited soliloquy, we shall be waiting.
On that matter, I am afraid that I must disappoint, for my own mediocrity in making such displays would be overshadowed by your own excellence therein.