I can't help thinking that there's an overwhelming number of difficult-to-decipher, difficult-to-write-in-shorthand symbols in the Promethean level and that there's an overwhelming number of symbols to memorize. I'm very uncomfortable with the multitude of commas that one is required to learn (in the single-symbol version). I doubt many Just Intonation composers and performers even consider those commas or think in terms of them; these commas have to do with the logic of the Sagittal system, and with JI and temperament theory.
I fear the multi-Sagittal accidentals would quickly become awkward. Johnston's notation does have the problem of long horizontal clusters of symbols but it uses also symbols as attachments (
would be used as the stem of
instead of having them side by side etc.), so this only applies to multiples of the same symbol ( +++ for 81^3, 77 for 49 etc.).
"A composer, or a reader who wants to analyse the score in terms of the prime lattice, may prefer the multi-Sagittal form. A performer may prefer the single-Sagittal form, depending on the instrument." It's difficult to say if there are singers or string players who'd prefer the former over the latter, as there is no JI repertoire published in Sagittal, except in Sagittal study materials and demos (as far as I know). It is a fact, on the other hand, that the scores of Johnston, Sabat etc. are written for musicians who tune the intervals by ear or are at least expected to do so, note against note, which is why the notation tells the tuning path exactly. That's why in Johnston, for example, a different symbol is used for 33:32 and 36:35 even if they're both quarter-tones and differ only about 4 cents. They're to all practical purposes the same interval. Sometimes they're even combined to the same accidental so that they cancel each other out (33:32 up and 36:35 down). It would be just fine to sing the uninflected note, but the singer wouldn't know how to find it if her note is the 11/8 of the 7th harmonic that's been sounding in the bass, say. That's the philosophy behind these JI notation systems: it's quite different from that of Sagittal, as I understand. Even if the accidental combinations get complicated, they're still preferable to numbers over or under the notes; all those off-stave markings are slow and difficult to read, and if the numbers are ratios, they require calculating, and if they're factorizations, they take up a lot of space. It's true that some performers (and composers) prefer 72-equal (Sims et al., the Austrian 72-toners) or 1200-equal (Johnny Reinhard, who notates in 24-equal with cent deviations above the notes) even for JI music. But a cellist friend of mine played a solo piece by Sims, in extended JI notated as 72-equal, and he found it quite annoying that the notation didn't tell which just interval each note represents. Originally, he tried finding the 72 equal steps and only later realized that the music is supposed to be played in pure intervals, but it took a lot of trial, error and analyzing. He'd prefer a Johnston-notated version of the Sims piece. The situation is somewhat similar here, the main difference being that in JI Sagittal (without the accents), the notation gives rational approximations for ratios, rather than the irrational ones of equal divisions.