That would be against the rules @EnergizedGamerYT

 

You can build a cobble only generator, but it cannot be automatic.

 

I'd like to add that something like this wouldn't even work on ECC.
As it changes the behavior or mechanics by creating ores that wouldn't spawn in vanilla Minecraft, the server simply wouldn't believe your game client, thus leaving you with ghost items (i.e. your client thinks it has an item, but as soon as you try to use it the server says that you don't actually have it).

Something like this would only work if implemented as a plugin on the server, not as a mod by players.