There are a few decisions left, but relatively few. What about +x weapons and armor? Is there only one +1 weapon in the world, one +2 weapon, etc., or is it that there's a +x weapon of each type (a +1 dagger, a +1 sword, etc.)? What about potions? What about scrolls?
There's no "right answer" here, of course. Here's how I'm planning on doing it. I'll be using the "Encyclopedia Magica" four volume set of magic items, and the tables in Volume 4 handily separate out the simple "+x weapon type" items from specific named weapons or weapons with specific qualities. I'll just be using the tables for specific items, treating each one as unique.
Potions I plan to make an exception to the rule: there can be multiple instances of potions. I like this for a few reasons. One, since I'll be going "one of a kind" with the availability of most spells in the setting at the start of the game, potions allow characters access to a few common, repeated effects. This takes the edge off the harder limits placed on spell availability. Also, potions are limited use items but are available regardless of class. They're also limited in terms of how many you can really expect to carry around at a given time, and they're often found in fragile containers. They strike a good balance: not likely to proliferate too much, but able to open up some of the possibilities that the "one of a kind" campaign framework otherwise restricts.
Alchemists can create the potions. For internal consistency, it may be necessary limit this "common set of potions" to the set of potions that can be created by an "Alchemist" character class. It may not do to have potions reproduce spell effects that are quite rare. Who is making these potions? Luckily, there have been four different versions of the alchemist class in various Dragon Magazine articles (issues #3, 45, 49, and 130), and I'm looking at those now.
Scrolls are another issue. But I'll push those off for when I'm talking about magic user spells.