Unless it’s part of some procedural tool or takes advantage of being part of a real time game engine, I don’t know why you’d want full modeling tools within a game engine. Nothing Epic could make as a 3D modeling feature withing UE4 is going to even compare or compete with an actual 3D modeling package. Designer Tools, to an artist, just looks slow and clunky. I get that using a separate modeling program is an extra step, but there’s so many free and cheap tools it feel’s too redundant and a waste of resources. There’s also blueprint construction scripts if you want to make assets that integrate into a level or scene without jumping back and forth between a 3d modeling application.
UE4 could always use more terrain tools. Epic has pumped some resources and tools into it, that was kinda the point of the Kite tech demo.