Oh yeah, is there a way to get diatonic notes to space evenly across staves so that they align vertically with chromatic notes spaced in between?
I would change the value and put the half notes in another voice (to preserve spacing) and remove (hide) the rests. Create the varying meters and hide the meters to create bar lines. Hide the stems in lower panel in Engrave mode. There may also be custom note heads you can use instead.
besides the first suggestion by @lafin, to use half notes on a second voice, and quarter notes, all with hidden stems, you could leave all in one voice, and to adjust the spacing, you could just set the Custom spacing ratio (in Layout options > Note Spacing) to 1, so that the half notes and the quarter notes will take the same space.
Method B (the better one, as @lafin’s second suggestion: no bar length difference problem; using all quarter notes and a custom Notehead Set):
To avoid different bar lengths is better to use white noteheads. I made a video on how to create a new Notehead Set with white noteheads that you can apply on the desired notes (you need to choose half oversized notehead because Dorico uses oversized notches as default):
Result (you can of course hide the Time Signature, as suggested above):
