Nice trickery Gryllus. The problem is that in 1 Tim 2:5 the sentence structure is totally
different than your sentence above:
εἷς γὰρ Θεός stands complete as is, there is nothing implied ( so no need for ἐν τῇ οὐσίᾳ ). It is simply saying that there is one God, as opposed to two or three Gods. It is not asserting that there is one God “in essence” ( whatever that means). Similarly, the second part of the verse is saying that there is one Mediator, as opposed to two or three. If εἷς γὰρ Θεός has an implied prepositional phrase, an awkward one at that, then why does not εἷς μεσίτης have one also ? Or does it ?
Also, I know you would like to change the subject to this, though you are not doing much better , but I am more concerned with the original issue we were discussing. About how a singular noun , pronoun or verb never denotes multiple persons in the Greek of the GNT.