Confessional Minimalism or Maximalism?

I have been thinking lately about the nature of the minister's relationship and obligation to the doctrinal standards of his church. Do we take a minimalist approach, which only asks that he not contradict the teaching of his confession, or is a maximalist approach to be preferred, which insists that he positively affirm his church's doctrines and promise not to stray outside the parameters of his confession?

Of the seven ordination vows a PCA minister must affirm, the second reads as follows:

Do you sincerely receive and adopt the Confession of Faith and the Catechisms of this Church, as containing the system of doctrine taught in the Holy Scriptures; and do you further promise that if at any time you find yourself out of accord with any of the fundamentals of this system of doctrine, you will on your own initiative, make known to your Presbytery the change which has taken place in your views since the assumption of this ordination vow?

In the light of this statement, one may reasonably enquire whether it is legitimate to posit an additional, supplementary version of a specific confessional doctrine which contradicts the confession's teaching, but claims the freedom to do so because it is just reflecting the broader teaching of Scripture on the subject in question.

For example, the Westminster Standards teach that union with Christ is a "special benefit" enjoyed by the "members of the invisible church," and that by this union "the elect... are spiritually and mystically, yet really and inseparably" joined with Christ (WLC 65-66). The "inseparable" nature of this union precludes "true believers" from "totally or finally falling away from a state of grace" (WLC 79). Finally, the various benefits of Christ's mediation, such as "justification, adoption, and sanctification," are given to "the members of the invisible church" as "manifestations of their union with him."

Now here's my question: If the phrase "union with Christ" is not found in the Bible, and if the various prepositional phrases used to denote this concept are also used in passages that plainly teach that the connection can be broken, then what is the responsibility of the expositor of Scripture at this point?

Should he (1) Teach that there are two kinds of "union with Christ," the Westminster kind and the John 15 kind? Or, (2) Teach that "union with Christ" refers to what the Standards are referring to, and insist that the John 15 phenomenon be called something else? Or, (3) Teach whatever version of "union with Christ" his passage is referring to without any qualification whatsoever?