Certain scholars contend that QEOS in Phil 2:13 is
both predicative and emphatic. Moreover, Stanley
Porter suggests that 2 Cor 5:19 serves as an example
of a periphrastic construction, although he adds: "there
is much controversy among grammarians and
commentators" concerning this text (Stanley Porter,
Idioms of the GNT, page 47).
I also find it interesting that Porter wants to render
2 Cor 5:19, "in Christ, God was reconciling the world
to himself." He thus seems to place emphasis on EN
XRISTWi, rather than the preverbal QEOS. And while it
seems that QEOS in 2 Cor 5:19-20 is possibly
predicative and emphatic, I think Colwell's rule is a
plausible explanation of the anarthrousness of QEOS,
which is evidently definite here and not qualitative.
On page 109 of Idioms, Porter discusses Greek
articular usage with linking verbs and suggests that
the construction IHSOUS ESTIN hO XRISTOS in Jn 20:31
should be construed "the Christ is Jesus" (taking
Christ as the subject). He makes this decision based
on McGaughy's rule, but 1 Jn 2:22 might serve as a
counter-example to Porter's argument.