so i would say give your users a way to customize the info displayed instead of having the display addon jump through hoops to format things
I'd rather impliment ways to change the data in my DOs rather than have Displays edit them for me. Now, that being said some authors would rather that way being "change line 32 from xxx to xxx" but that's not necessarily a bad thing.
I'm seeing the type attribute for exactly this type of thing. If the Display doesn't check the type then it's the Display's problem. Just pick a type and go to town imo, publish what you expect the spec to be for that type.