Tracking all loot is a bit much but say in other systems like critical hits I know blizzard has had a history of preventing outliers, because chance is chance and while unlikely you 'could' be exceptionally unlucky and that wasn't fun / feel good.

Your idea certainly could help so long as someone is willing to hold onto everything to laser down the RNG.

In the past in order to "2 birds 1 stone" a glamour log and RNG thought of a crystal library and aether forge, where the long and short was almost all content rewards could be broken down into materia (aether) of that space. Let's say the The Tower of Babil, which has gear drops meaning a lot of potential gear. The scouting boots drop which you don't need, so you compress it into The Tower of Babil aether. You get back and you can exchange it to the GC for GC tokens (making a convenient stack possible), or you could de-synthesize it for a larger pool of random materials (if you were looking for specific materials it might be better not to stack them as such). Yet more importantly you decide rather than that you collect them till some threshold X, and you go into the crystal library (imo think Chrono Trigger end of time, but whatever works lol) and you trade those X aethers to unlock ALL the glamours of that content in your glamour log. It is now effectively 1 variable "1/0" representing 20+ potential visuals. However, another thing you could do is take those essences and exchange them for items from that content, like armor, cards, etc. Before you unlock the glamour set it might be more expensive, but afterwards it would be significantly cheaper.

May use the items in crafts, quests, relics, etc, as well since it's available.

Sort of a memory cheap way of getting both a glamour log and RNG control. To help with new content could keep that space locked until determined period of time (players on the edge of content might have to have content last longer, even if it's via a unfortunate grind).

Had concerns for Blue Mage as well, where I personally had solo'd Ifrit around 40-50 times... and that was very annoying. I thought Libra / Condensed Libra could be used to help with chance learning, with perhaps two different styles where one is if they cast it during the debuff and the other being a buff on your character that tracks failed spell learnings, increasing per stack, and then resets once you learn a spell.