My advice: Don't try. Write markup for overriding the 'text property.
And if you don't feel up to doing that sort of markup,
you could get most of the way with an additional context:
%%%%%%%%%%%%%%%%%%%%
\version "2.20.0"
coharmonies = \chordmode { d1:m s d:dim s fis}
harmonies = \chordmode { c1 c:m c:7 cis c:m7 }
\score {
<<
\new ChordNames { \coharmonies }
\new ChordNames { \harmonies }
>>
\layout{ }
\midi { }
}
%%%%%%%%%%%%%%%%%%%%
Cheers,
Robin
