Oh god that's so much worse.
It's not that the backend code is unmanageable, it's that they have no concept of how a database works.
There is an unofficial plugin for the game that does exactly this, so that's fairly head scratching.
"Adds and indicator in item tooltips to show whether you have acquired that item.
This indicator is in the item's description near the bottom and only appears for items that are unlockable, such as orchestrion rolls, minions, etc."
The proof: https://goatcorp.github.io/DalamudPlugins/plugins
Search for "Good Memory"
You probably don't want to be linking that here.
I'm not claiming to use it, I don't have any screenshots of what it looks like in game and honestly couldn't describe it to you. I just know that it exists.