In my mod to add Mekanism's 4 chemicals as AEKeyTypes, I have found that the existing API isn't good enough for such a task while being on-par with the standard item and fluid keys

1. Lack of world interactions
   It's impossible to actually have a custom type in the system, such as with a storage bus. The StackWorldBehaviors class looks promising but most of the dependent interfaces are sealed off, along with StackWorldBehaviors itself being non-API.

2. Pattern provider return inventories and interfaces are hardcoded for the ItemVariant and FluidVariant storages, so they cannot be made to accept other lookups through the API

3. Lack of menu interactions
   It's not possible through the API to declare how a container can be emptied or filled into the system through the UI provided by terminals, pattern providers and interfaces

4. Lack of support in pattern providers
   Pattern providers are hardcoded to fast fail on non-standard AEKeyTypes, for the system not knowing how to push non-standard AEKeys. Related to point 2

Also, adding lookup for matter condenser would also be useful, as matter condenser and storage bus is the usual way of handling overflow