Where does the principle of applying the concept of model ... come from?
I think your question is caused by a misunderstanding of English language.
I speak German (not English) and work in the field of electrical engineering. In the university we were told what the German word "Modell" (English: "model") means:
A model is a simplification of something, which contains all important aspects of the thing which is described but which does not contain any unimportant aspects.
If someone asks you what the Russian Orthodox Church is, you might answer: "This Church has about 250 million members. One of them is Jekaterina A. She is not very interested in the mass. Sometimes she even begins sleeping during the mass. Then there is Dimitrij B. He prays very often and often attends the mass early in the morning ..."
The person having asked you will of course not be interested in that. Therefore you will not answer this way but your answer will only cover the important aspects of what the Russian Orthodox Church is.
(In an answer that completely describes the Russian Orthodox Church you would have to describe all 250 million members!)
However, because you left out all of these unimportant aspects in your answer, your answer will be a "model" according to the definition we learned in university.
... ModelS of ...
Of course when answering different questions, different aspects may be important or unimportant:
Answering a question about theological differences between the Catholic and the Orthodox Church, and another question about the number of members of these Churches, completely different aspects will be "important aspects".
So for different questions different "models" exist.
Did anybody try to apply the concept of scientific model to any theological notion before Dulles, or he was the first who did so?
I don't know who was the first one that used the word "model" in this context.
However, we find early descriptions about what "the Church" is in the letters of St. Paul in the Bible.
So using "models" to describe the Church is as old as the Church itself.