I did it earlier in this thread but will do it again.
Here are the common traits between all IO (per what has been stated)
- Contain one or more member country
- Have a button to access (called a control group)
- Formed in script instead of hard coded
- Must be predefined outside of the game
- Are not playable entitles / Do not count as countries
- Have a unique UI*
- Have a unique map mode*
- Exist as a design tool to add flavor
- Does not block access to other IO^
'*' = For IO that can have multiple instances item may be shared between them. For example, all "Unions" sharing the same UI.
"^" = IO will be blocked access to multiple instances of the same IO. Cannot be part of two "Unions". Cannot be part of two Patriarchates.