I have a few theories about this at current, but I just wanted to compare with others. What does Arcane Sanctum give you with its rating.... does it mean you always have ingredients for spells up to its rank?
No, that's based on your Lore
"You can move straight into the casting stage if the spell’s complexity is equal to or less than your Lore (after it’s adjusted by focus items—see page 278). This indicates that your wizard’s personal collection of knowledge and accoutrements suffices for the spell."
Honestly, it doesn't appear to do anything ... the term "Arcane Sanctum" doesn't appear anywhere in YS outside that table in the Resources skill (I searched my pdf copy), and I read through the thaumaturgy preparation rules and don't see anything about it.
Workspaces are fairly silly anyway, like the guidelines on libraries (the bit about the Internet being a Mediocre library is just ridiculous... I can see that you can find some specific things, like non-open-access scientific papers, in a good university library that you can't online... but even so that would probably make it Fair-Good by the listed guidelines. And even that isn't really accurate if what you really care about is finding the information itself rather than being able to cite the original source... anybody with a good Scholarship score should know how to judge the quality of online sources.)