How do you understand:
Eph 3:3-6,
3 How that by revelation he made known unto me the mystery; (as I wrote afore in few words,
4 Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)
5 Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;
6 That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:
Rom 16:25,
Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began,
Taking it for what it says, I would say that there is something about our present age that nobody knew about until it was revealed to Paul, namely something about Gentiles being fellowheirs and of one body, i.e. the church. Therefore anything read
into the OT about the church is just that; r
eading into the scriptures, otherwise knows as eisegesis.