Phoenix Downs are a problem. Are they made with Phoenix feathers? Where do Phoenixes fit into the FFVII world? Why does throwing feathers on an unconscious person wake them up? Or is it a drink? How do you get an unconscious person to drink? Are there curative properties, and if so, what differs them from potions? From Hi-Potions, X-Potions, Elixirs, Megalixirs? Why is this an item I care about?
These are all great questions and ones I would love to develop for a speculative encyclopaedia of FFVII. Unfortunately, modern readers don't seem to give a crap. Since the LotR movies came out, no one reads the books anymore. That's a shame. but it's a different time, I guess. That's why I have forums like TLS where I can talk about this stuff to no end
So getting into details about items that have nothing to do with the plot just get in the way. It creates a barrier between author and reader, and the work becomes "Self-indulgent." Harumph.
If I were novelizing FFV, however, Phoenix Downs would have shitloads of development, because they use them in the story. Just as I would develop Softs for FFIX. Those items make those stories special, but in FFVII, they're just there for battle mechanics.
Materia is what FFVII brings to the table, and that's what should be focused on in the telling of the story -- as far as items and equipment go. Materia has an interesting methodology, history, and plot significance, and it has the opportunity to make every battle scene in the series stand out from every battle scene in every other fantasy novel. The distribution of potions, softs and ethers -- comparitively -- clutters it up.