You'd have to be able to, e.g., Command-Click to multi-select methods and then when you paste you'd have to remember to do any needed modifications on every pasted copy.
My main use case so far for copy / paste of a method is to move something, say, out of a class and into a module so it can be used anywhere (copy & paste, then delete the original). Because you realize that where you defined it wasn't the best location, or the method has more general utility than you at first thought, or it can be easily generalized.
I could see your use case if it wasn't pure copy/pasta = code smell, e.g., there's method call you want to attach to all the controls, rather than multiple lines of code.
Now that you could, I believe, script multiple copy / paste operations, would that possibly cover your particular use case? That would formalize and systematize such an operation. Another scripting option might be, "put this function call in event X of all the selected controls".