I have a poor mans version of this made with Fastify, but it would be great to see a completely native REST server with OpenAPI 3.0 built in, and the only means to create routes.
At one of my jobs I actually tasked an engineer to build this for our express servers and it always stunned new engineers that they had to build the API spec before PR, otherwise the tests auto fail. It also required both input and output validated, it made integrations a dream.