Do you think this formula would also be compatible with (or benefit from) some CaCl2?
Compatible yes, benefit no. Only reason I see to do it is if trying to limit NO3 levels while maintaining high Ca levels, which would be to satisfy some pseudo-scientific notion about Brix, or plant defenses, or senescence, etc. No real legitimate reason not to get all Ca levels from CalciNit if using solutes, the plants N requirements are always greater than its Ca requirements.
Also, I understand that sulfur plays an important role in flavor - and always thought there was good reason to use it later into flower - hence boosting epsoms at the end. Here we're pulling back on sulfur. Is this by design or a side effect of boosting phosphorus while keeping its attached cation, ammonium, at the same level?
Its a side effect of boosting phosphorous while keeping NH4 in check. The S being essential for flavor is a popular notion that AFAIK originated from that fact that certain crops like Brassica family and Allium genus vegetables (mustard and garlic families essentially) have huge S requirements for the production of the crops essential oils and organosulfurs that make up the main constituents of those particular crops flavors. Someone decided that that may have some relevance to cannabis and boom, the S = flavor notion was born. It almost makes sense since S is required in large amounts to create
terpenes and terpenoids (Mevalonate and Non-mevalonate pathways), but then again N and P are required in even greater amounts for terpene/terpenoid synthesis, and you don't see anyone preaching N for flavor.
Ive grown crops providing ~30, ~ 60 and ~120ppm S in fertigations the whole grow and was not able to discern any differences in plant growth or quality (potency, smell, taste) of the final product. I personally do not believe that level of S fertigation has much effect on final flavor, but that's just my personal knowledge and experience, not saying its 100% bullshit.