Yeah, most of me teaching myself how to use the editor when the game came out was by looking at base game scenes to see what the devs did, so having access to more of the scenes terrain would make it a lot easier to pick apart what devs were doing. For battle scenes its not as big of a deal, but for more detailed scenes like cities having to use the navmesh as an indicator of where the terrain is supposed to be is very annoying.
Even if we cant get all the scenes SED (like NPC mentioned, the filesize might be an issue), I think a good start would just to have more scene's SED, especially smaller scenes like arenas and hideouts (especially hideouts considering the contest).