I have to admit that I am not fully understanding your question. Would you want to write a plugin with a widget to accomplish your task?
*What are you trying to do?
Usually I find that if I need to loop outside the loop, that I have to define which categories apply and which do not, usually for me another loop that is outside the Wordpress default loop. I am working with an example of article loops and I hope to update this answer before it is fully complete.
For those voting - please wait until I have a complete answer available before voting. I hope to take the updates to the question and update the answer accordingly.
Thank you for asking your question.