Excommunicate all without exception!
And there's more
"Confusing this 'union with Christ' with visible membership in the body of Christ through outward profession or sacramental expression is a serious error and endangers our church's faithful testimony to the Gospel essential of justification by faith alone." (lines 24-27, page 2214, of PCA on FV).
The force of the argument seems to be that we must not give the sacraments to those who are not elect. But the only way to avoid this, with no risk of false positives, is to give the sacraments to nobody at all. It's back to God's secret counsel again.
But the NT clearly does not say that we don't treat anyone as elect for risk of getting it wrong. At this point, covenantal objectivity is one way to go, and there have been others suggested. But if it is paramount to avoid treating someone who is not decretally elect as though they were, we're stuck with a null church.