Special:EntityData is intended to be a LinkedData interface.
It should support various RDF flavours, and plain JSON.
Other formats (based on MediaWiki API result formats) should be dropped (currently, php-serialized is allowed per default).
This would allow us to use the JSON serialization of the entity directly, and drop the clunky dependency on the API result formatters.
TODO reasons we want to drop it
Notes:
- needs to go through the breaking change process