All translations --each and every one of them, need constant revision.
The term 'word-for-word' needs to be retired since no translation lives up to that simplistic and naive ideal.
But you gave two examples --the NKJV and the NASB. They certainly would be strengthened with thorough revisions. And when completed they would no longer be considered remotely 'word-for-word.' They would then be in the category of mediating translations --a very fine place to be --actually a sweet spot.
Listen, all translations do to varying degrees what the NIV states in its preface.
"Faithful communication of the meaning of the writers of the Bible demands frequent modifications in sentence structure and constant regard for the contextual meanings of words."
All Bible translations do that in greater or lesser degrees. It's just that the translators of the NIV are more honest than most PR departments of various competing Bible versions. 'Optimal equivalence' and 'essentially literal' also need to vanish as ways of describing translational methodology.
There is still a distinct difference though between a formal translation and a thought for thought version, and while the mediating position seems to be what many prefer, the truth is still that those versions such as the Nas and Nkjv editions do tend to overall give to us in English what the intended meaning and message of the scriptures are to us...