Unbuilt carrier and commerce-raider matchups worth studying

Which unbuilt or underused warship classes would be most useful to see tested in service?

The Malta class, a completed German carrier, and an Alaska-class ship facing a genuine commerce raider would all answer important design questions.

The unrealized ships chosen here are interesting for what they could teach rather than for spectacle alone. The Malta class would show how Britain's large carrier concept developed. A completed German carrier would reveal how an institution with weak carrier experience actually operated a poor design. The Alaska class could also meet the serious commerce raider it was meant to counter, placing a ship often judged in isolation into its intended tactical problem.