I understood, but you use mission editor to edit terrain which is internal. I don't know if mission editor propagates changes in multiplayer automatically but if the issue here is time-to-edit, consider the fact that building a mountain in mission editor from completely flat terrain takes about a minute.
The only game modes that have used dynamic terrain modification at runtime are like... trench warfare? Mining? Not exactly the cutting edge when it comes to beautiful looking graphics, and you didn't need to remove terrain to accomplish voxels. In-fact V21 was historically a problem for mining servers because Badspot stubbornly refused to make the ground plate removeable for a very long time lol.
