It might be helpful to compare how the full blown Catholic understanding, say, of Mary developed out of the Scriptural and early Christian understanding of Mary with the way an oak tree develops from an acorn. In each case, the before and after look different but are essentially the same. And one naturally leads to the other just as promise leads naturally (on a good day) to fulfillment.
Commentary and discussion regarding science, faith and culture by Leo White
Comments
So the Old Eve / New Eve contrast alluded to, I think by Iraneaus (or was it Ignatius -- I get those two guys mixed up) is a kind of acorn from which the doctrine of the Immaculate Conception developed.
As for intercession of the saints, that is very, very helpful inasmuch as it undercuts the possible claim that the Catholic focus on the saints is an adaptation of the Roman Pantheon. But if ancient Jews understood Elijah as you say, then the doctrine of intercession was already "oakie" to begin with (I probably should avoid such wordplay when in Oklahoma).