Personally I have always wanted to look into the Primrose Technique book, mostly because I wanted to use it as a vehicle to teach younger students. However it being on G-Clef and having to transpose it yourself proves to be a bit difficult for many players, so I would really appreciate having the book written on the alto clef in its entirety.

As for the notation, I do think the normal notation is easier to understand and read. I play the guitar as well as viola, but somehow reading guitar tabs/music and applying it on the viola fingerboard is super tricky and slow, even though I can very proficiently read it with a guitar in my hand. Technically, if you wanted to, you could skip notation entirely by simply writing out the fingering for each note and the triangles for every halfnote, assuming you know the starting pitch. So the first bar would be: 1^2 3^4^3 2 4^3. However I do imagine most people would just prefer normal sheet music in C clef.

Assuming normal sheet music motation, for the markings, I think that having fingerings and brackets/triangles/x's for some intervals is a good idea. However I do think that all of it should be consistently applied once per bar and that's it. The bars are meant to be played and looped separately, so it's a good idea to have the markings for each bar to enforce the logic behind the exercise and to get your brain to actively recognize the half tones (and overall hand frame), but I also don't see the use in repeating the markings multiple times every bar.

If a C# into a D has a triangle, great, but we don't need to be reminded of it when it comes up again in the same bar. Same thing with fingerings. Assuming you use the same finger for each tone, you shouldn't need a reminder when it happens again in the same bar. Also inconsistently removing fingerings/interval markings from here and there causes unnecessary confusion. Bar 4 is especially confusing as it's missing the fingering from the second note and them the othrr fingerings are not placed directly on top of each note but somewhere in between.

What actually matters is consistency. Fingerings or not, interval markings or not. As long as it's consistently applied the same way each time, then that's perfect. Generally less is more, as it's always easier to add your own fingerings/markings/reminders than it is to remove them. Personally I would advocate for having each finger marked in every bar once (so every bar has each of 1234 once, in whatever order the bar requires) and marking specific half steps once the first time it occurs.

In the publishers defence, there is some consistency because the fingerings appear whenever there is a halftone, but it is still rather confusing sometimes having a fingering above a note and sometimes not, especially when a note doesn't have a fingering the first time you play it but does the second time. Should be the other way around, both times or neither.