Add more view modes support, even for content that is not an Entity. Boost multi-site search support massively. In order to allow external data to be shown better, we need a way to show this data in view modes without them being entities. Perhaps even fake entities? I'm not entirely sure what this story should like like but we should certainly discuss it.
The broader picture here is that multisite search in Search API is currently unrepresented and should get an overhaul
User interface changes