There is nothing "wrong" with the KJV, it's just that people ignore the fact that in the KJV "YOU" is always PLURAL. So "within YOU" is the same as "in your midst".
For sure, this notion that "the KJV failed to properly translate this here, that there" and so on, is base ignorance.
The Early Modern English of the KJV is over four hundred years old, more or less. The "failure" is not in the translation, rather; in the level of competence or incompetence of the particular reader as to its Early Modern English.
And that is only half the story. For the fact of the matter is that the intended sense of words is determined by who is using them, when, where, how, and why, they are.
In this, the issue is never the issue of the translation of one word or words, rather; of intended sense, as determined by who is using them, when, where, how, and why they are.
This is a Basic Principle of language in general, that, when taken to be a principle, or general rule of thumb to be consistently followed; began to lead to the re-emergence of the Mid-Acts Hermeneutic [Acts 9 Dispensationalism].
Some, however, go by the end result of other's labors, and as a result; never really make the root principle their own.
The result being; that they ever remain unable to progress further in their own understanding of the actual dynamic at work behind words that gives them their intended sense regardless of "translation."
In contrast to others who; seeking to go by the original root principle as to how words derive their intended sense, as a result; are ever able to continue to further refine their understanding.
Books about this, or that, have their place.
But far too often they end up a crutch - what to think, in contrast to personally getting in the Text [Scripture] one self and There wrestle with It one on One, not only for Its Intended Sense, but for Its Principles.
As fascinating as books are and can be; they too often end up, in the hands of far too many, all they actually know "about" a thing...
And what that leads to - an all far too common all knowing narcissism not unlike that of the Adversary's moment before that sea of glass.
That moment when, seeing his own reflection together with the sum of his wisdom; he concluded that wisdom of the wise God would prove foolish in a Mystery - "I will be like the Most High."
Keep your books you who are made wise in your own conceits by your overreliance on them.
Some of us are doing just fine in the promise that is 2 Timothy 3:16-17 - just fine...as is.