That's quite a novel argument, saying that 2 Timothy 3:16-17 is "a form of the prophetic present". I never heard that one before. But the problem is, Scripture doesn't say or even imply that. There's a much simpler explanation, which is what I have been trying to steer you towards.
In the previous verse (2 Timothy 3:15) Paul is telling Timothy that "from thy infancy thou hast known the holy scriptures which can instruct thee to salvation by the faith which is in Christ Jesus." This verse is specific, the Scriptures that Timothy had since his infancy is what we call the Old Testament (Talmud, Tanakh, whatever..). And it is of these Scriptures that Paul is saying that they can "instruct to salvation".
Then in the next two verses Paul is moving from the specific situation of Timothy to the general rule, explaining if you wish why he said what he said in verse 15: not just this or that book, but
all Scripture is inspired, profitable etc.. It does not make sense to argue that Paul was speaking about the "total number of 66 books, and nothing more or nothing less", since some of these books were not written yet, and Paul even doubted whether his own writings were inspired. They were, but he didn't know that.
Paul was simply explaining that the nature of Scripture is such that it is inspired, and as you pointed out, the purpose and the effects of something that is inspired is that it is profitable to use and able to produce the effects mentioned (being perfect, every good faith.. I mean work).
Another way of looking at it then is this. What is true of the nature of a thing is true of every thing of that nature. When we say apples grow on trees, then we know that each and every apple grew on a tree. Apple 1 grew on a tree, apple 2 grew on a tree,.. apple 37,763,774 grew on a tree, etc..
Apply this to what Paul is saying here:
- The book of Genesis is inspired, profitable to teach.. that the man of God may be perfect, furnished to every good work.
- The book of Exodus is inspired, profitable to teach.. that the man of God may be perfect, furnished to every good work.
- The book of Leviticus is inspired, profitable to teach.. that the man of God may be perfect, furnished to every good work.
- ...
- The Gospel of St. John is inspired, profitable to teach.. that the man of God may be perfect, furnished to every good work.
- ...
- The Epistle of St Paul to the Corinthians is inspired, profitable to teach.. that the man of God may be perfect, furnished to every good work.
- ...
- The book of Revelation is inspired, profitable to teach.. that the man of God may be perfect, furnished to every good work.
When a Protestant tries to insert the word sufficient into 2 Timothy 3:16-17, he is forced to insert the same word into each of the above statements:
- The book of Genesis is sufficient..
- The book of Exodus is sufficient..
- The book of Leviticus is sufficient..
- ...
- The book of Revelation is sufficient..
Does that makes sense? No. That is NOT the meaning that Paul could have been trying to convey here.
Protestants then will try to argue, "well, Paul switched in the middle of his statement from speaking about the nature of Scripture to speaking specifically about the 66 books that some Christians one day will proclaim as inspired."
And this I believe that is what Patrick Madrid called an error against the
hermeneutic of anachronism, or in simple terms, reading something into Scripture that simply is not there and could not have been there.
So, there is no way you can argue that Paul is implying sufficiency in 2 Timothy 3:16-17.