After reading through the Arc section of the manual and playing around with Orca using Arc (and switching back and forth with Grid), here's what I think.
The preset sets concept is not for everyone. If I have created a patch using a Grid but want to improvise with it, using Arc, I don't want to turn a dial and completely lose the framework I've created. I like the idea of rotating, and editing on the fly, but personally I don't want to have to choose from preset sets of divisors and phases. Some people might want that, though.
I think we have to accept that we can't do everything with Arc, and so I suggest we have it do the things it's good at - setting and displaying divisors, rotation of scales and weights, choosing presets and scales, NOT editing or creating scales...
Here's what I propose.
5 pages instead of 4, but all very simple
Page 1 - Divisors 1-4 (displays the tracks only, no back and forth)
Page 2 - Phases 1-4 (displays the tracks only, no back and forth)
Page 3 - Scale A, Scale B, Bank, Preset (same display concept as currently implemented, just splitting presets into banks and presets)
Page 4 - Rotate Scale A, Rotate Scale B, Rotate Weights, Global Reset (same display concept as currently implemented)
Page 5 - Divisor sets, Phase sets, CV A/B sets, Mutate (same display concepts as current page 1)
Knowing what page you're on isn't simple. I suggest that each time one hot swaps back to the Arc, it reverts to page 1. Hitting a button a couple of times is no problem if you know where you are.