Idea is cool, but we don't have the technical ability to alter maps that way. We've discussed this before internally.
We would have to make a separate map for each tier selection and design balance for a separate list of enemy ships on each one of them. We'll bring back the old ops with a new difficulty level and see how popular they are and then see how we can add to the replayability.
Thank you for the suggestion though and hope you'll try the ops with the new settings when they come back.