the only viable alternative I see is the one I mentioned above.
A dumbed-down version of UE4 provided by Epic to developers ensures Epic themselves control how much the “UE4-game editor” contains from the full UE4, saves developers the time of having to code a custom editor, and removes all barriers for mappers and modders.
in fact doing it this way might even be beneficial for Epic. how many people started using the UT3 editor, only to move to UDK when it was made available? if modders realize that UE4 is a much more powerful version of their beloved ‘Game X Editor’, they might consider moving on to make their own games with UE4