I would love a feature that would allow me to select some areas from the world editor and copy-paste them elsewhere or in another world. (idealy with the objects on them also, but just the terrain would be wonderful too)

This would allow editing new portions of the map safely and just paste the result in the final map when it's done; it would be great when working in team too, and also it would if you would decide to "shift" a zone on your map further on (say you want to make a river between two mountains but realise too late that the mountains are too far apart; this tool could also allow you o shit them closer).

It may be complicated, so I won't insist, but this could help me out very very much! So the main benefits would be:
- safe(er) world editing
- could use "world templates"
- area shifting

Let me know if there's any chance for us to get this feature.

You could do most of that using the Editor Network Interface
Definitely the terrain, as all functions for that are provided, as for the objects, then the only thing you can't do at the moment is specify object parameters, but you can set the most important thing (base object, mesh/phys body, etc)