One of the problems that we have right now with the configuration of the search page, its just a bunch of dry text, so it requires a lot of energy and processing from someone to find what they are looking for. With tiles, you could interleave other wikis, while also giving some kind of opportunity for things to "Jump out" as exciting or engaging.
If we do do tiles, I think there needs to be some type of extra visual design that seperates Wikipedia articles from the other projects however: maybe a color change in the box characteristics, or distinct prominent placement of project labels, or something to that effect.
I also am not sold on seperating the results into tabs: folks don't know about these other projects yet, so if we leave it all up to their own decision making (having to choose the results from the other project, to see them), its going to get neglected like so many other features on the projects. There needs to be a little bit of forced exposure, to make this search change impactful for the smaller projects.