Using one exercise to practice a multitude of techniques

Byzantine, Arabic or double harmonic scale

I quite like doing exercises - there is a certain meditative quality to working on an individual skill repeatedly to get it exactly right.   And finally nailing an exercise is nice because I can more predictably repeat it than I can with pieces (where skills that I thought were nailed disappear into the ether on a regular basis).  However I'm much more likely to stick with an exercise if there is a reason for working on it, like it's a component of  a piece I'm working on.  For instance, in my long- sidelined VL4 prelude, I'm practicing the moving arpeggios by just fretting the bass note, which essentially turns it into a single string exercise for the left hand.   Now just repeating this over and over is kind of boring, and knowing me I will eventually 'forget' to practice it if it's too boring.

But, then I started to think about all the things I could practice while working on the LH movement - first of course, was learning the LH pattern. Then I figured I could practice the LH movement by doing scales on a single string - why not? And review modes while I was at it - E major, plus Lydian and Mixolydian because they are based on the major scale.   Natural minor and harmonic and melodic minors plus Phrygian, Dorian, and at a pinch Locrian, because they are based on the natural minor scale.   At least that's the way I think of them.  There's a nice description here.  I never could come to grips with modes by 'starting on a different scale degree.' Although I understood the theory, translating it to the guitar was a bit like the relationship between understanding that german verbs go at the end of the sentence and speaking fluent german. And besides which, I could never remember the order they come in (essential to knowing which scale degree to start on).   I'm not the only one - I know someone who finally figured out modes when they were able to relate them to pentatonic scales (see a description here), although this definitely wouldn't work for me because I don't know my pentatonic scales...yet ( I guess I could practice them on a single string!)   However I have internalized the intervals in major  (WWHWWWH) and  minor (WHWWHWW) scales so on a single string it's pretty easy to take a major scale and raise the 4th (Lydian) or lower the 7th (Mixolydian) for example, cos I can count up to 7. 😊   Maybe I'll eventually recognize them by ear - I live in hope.
For the RH I could emphasize different fingers, which might be useful because the bass note needs to be brought out for the melody and currently I'm losing the other notes when I do that.  And of course dynamics pertinent to the piece.

Hopefully making it interesting, and relevant to a current piece will make me stick with it long enough to make progress, and as a bonus I might finally learn that weirdly compelling byzantine scale...