New command for mapmaker /fillstructurearea /fillspawnerarea

For creating worlds, I would like a command with which you can create the structural area. For example, the special area of ​​the witch's hut or the area of ​​Nether Fortress.
For this I suggest the command "/fillstructurarea" for.
A command where you can directly adjust the spawn behavior over an area would be an ingenious addition. 
For this I suggest the command “/fillspawnerarea”.

Thank you for supporting this idea