So it occurs to me that there are two Daedra for the Aedra (16 / 8 or 9) and that their spheres tend to overlap. For example:

Arkay / Meridia / Azura* (Azura is sketchy because could be in another trinity): a trinity of cycles of life, death, day/night etc.

Dibella / Sanguine / Sheogorath: beauty, pleasure (madness is connected with art in SI).

Julianos / Hermaeus Mora / Azura (or Nocturnal or possibly Mephala): magic, knowledge especially forbidden knowledge

Some trinities are more dubious than others, but the Arkay one seems pretty solid to me. Thoughts?

Interesting semi-isotropic triangle theory you have there, I'll have to look into it further.

It's a thought that's occurred to me as well, and I've always been a fan of it.

Shezarr/Mehrunes Dagon/Boethiah: Ambition/Revolution/Change

Kynareth/Meridia/Hircine: Interactions with nature