Good idea I don't know if it would be easy though to make an "easy" map maker.
It isen't, and it woulden't really be worthwhile for this game anyway.
EZ-Mapping tools work best for simple arcade games, think TrackMania or LittleBigPlanet, something that has a simple artstyle, and where it doesen't really matter is the maps look very similar, because it's all about the gameplay.
RO2 is not that kind of game, it's a game that relies heavilly on player immersion, the maps need to look like real places as much as possible, so stock terrains and copy-pasted decorations and buildings just aren't going to cut it, it's just never going to come clouse to what a skilled mapper can do with the full editor, the standard RO2 maps, and maps build with the full editor would just be so much better than any EZ-made map, that nobody would bother playing the EZ ones, making the whole thing pointless, and a massive waste of development time.