Well, we supposed to come from monkeys so after all that could be a good thing to do following your example 
Thanks for your reply! I’m trying it out but what can I do if I want to change the whole embed.rb file?
I see that can only be used to replace an specific class but I want to replace the embed completely removing the buttons and showing a simple onebox.
I can work on the file but I don’t know how to put that file into Discourse without forking (that seems to be gorilla patching).