This is in relation to my last question about chord-scales. I was wondering if secondary dominants enable an application of chord-scale theory that would allow me to expand an existing chord progression by adding new chords to a song. I'm asking about using chord-scale theory to improvise a new (or expanded) chord progression while soloing over a song.
As background, a secondary dominant is the V chord of a target chord. When we select a scale for the secondary dominant, we can think of the secondary dominant as being the V of a new tonal center we temporarily establish. But establishing that new tonal center (or key) sounds to me like a possible theoretical reason to justify other chord-scale selections. So couldn't I add other chords in order to improvise a whole progression in that new scale/key? For example, in addition to the V of the new key, could I add a ii chord, a iii chord, etc. of that new tonal center and effectively extend that tonal center for a while before returning to my original chord progression?
When soloing, do musicians (e.g., in the rhythm section) consider a particular chord-scale selection to determine what additional chords they could improvise?
Edit: I think chord-scales establish modes as the new scales, whereas secondary dominants establish a chord as the new scale.
Edit#2: Secondary dominants are different than chord-scales in that chord-scales are diatonic (and use modes) whereas secondary dominants are chromatic (go outside of the key). I got this a bit mixed up when I asked this question.