While maturity is in some ways a synonym of completion, you are making both synonyms of perfection. To me, that's a stretch. I think it's fine to say that maturity and completion may be
likened to perfection, but are not true synonyms. To me, Eph. 4 is clearly discussing believers, not the Scripture. I think that if Paul meant the completion of the Canon here, he would have specified it (same thing for 1 Cor. 13).
Further, in order for this to resonate with me, the maturity spoken of in Eph. 4 could not involve an ongoing "attaining to". New Christians are constantly coming along the path to maturity, but aren't there yet. I suspect you would agree with me that the Church as a whole has not reached the unity of the faith, but are in need of being built up, equipped, and taught... which is why we still need the "equipping gifts".
If the gifts which God gave to the early Church "were completely associated with the revelation of His Word in the bible", why aren't the prophecies of Philip's daughters recorded? That they prophesied would be completely irrelevant... and I don't believe there is
anything irrelevant in Scripture. Also, what would the death of the apostles have to do with anything, as the Canon was complete before the death of the last one, but after the deaths of several others?
I see the way that cessationists understand both prophecy and knowledge is extremely limiting. I can't think of a single person who has ever, in my firsthand experience, claimed that the "words" so given are equal to Scripture. Do people abuse them... yes, but that doesn't invalidate them any more than speeding invalidates automobiles. The Bible contains all the knowledge that a person needs to come to salvation and spiritual maturity (on that I hope we can agree!), but it clearly does not contain all the knowledge there is. I don't see anything in Scripture to support such a narrow view of these particular gifts. I believe that God uses them gift to convey information which could not or would not be known either through Scripture or in the natural.