Ability for modders an coders to add their own displays to the general game screen (the play screen how I call it) and manipulate it like the "Advanced HUD" mod does.
A general class with a .addDisplay() method to add InterfaceDisplays that show the content you would like to display.
The content could be just an icon to display some kind of state the player currently has, text overlay, or a completely differnt thing
Possible additions would be an option to specify a top/center/bottom and left/center/right for where to display (Like "snap" to the window borders and define an offset: TOP_RIGHT with a 5px margin).
Justification and Use Case
Many mods/plugins already add their own interface elements to display "mana bars" or extended inventory placeholders, by adding an API their would be less conflicts if more than one mod tries to add stuff to the play screen.
If two mods try to edit the inventory bar - which mod is getting the priority?