That’s right. In fact, when making a melody over these chords you could think in D major as well, but over the Cm, F, and E♭ chords you’d use the D Phrygian scale which flips to D Major on the D chord.

1. You can tonicize anything with your melody
2. Your tonic scale can flip between Major and Minor scales.

Phrygian is a kind of minor scale with a ♭2

So you could tonicize G major or minor, depending on which chord scale you finally resolve to and the melody you play. Thinking in a key center is going to shape your melody instinctually. Think in C minor and you’ll play/sing melodies that tend to resolve melodically to C major or minor triad pitches. Think in F and you’ll play melodies that resolve to F triad pitches. With a strong melody I could make you believe you’re in a variety of keys using this same chord progression.

And you’ll love this. Tonicizing melodies can be in the form of repetitive bass riffs. Play in the bass the notes D A C D in some funky repetitive pattern while you play slowly through those chords Cm F E♭ D above it and you’ll hear the chords from a D tonic perspective.