I feel that way about the idea of coming up with a simple tune after going deaf, but hearing a full symphony you're composing while deaf is a whole new level.
Then again, despite being a professional singer when I was young and then attempting to study composing I discovered I have no skill for it - so composing even a simple orchestral piece without being deaf seems complex to me.
It's not that hard if you have a theory of music like a pro like Beethoven does. It's like writing a program. You aren't picking a note at a time, you are laying down "tracks" with parameters.
Then again, despite being a professional singer when I was young and then attempting to study composing I discovered I have no skill for it - so composing even a simple orchestral piece without being deaf seems complex to me.