The cost of making the tender a submarine

Could the submarine tender itself be a submarine?

A tender for modern boats would need an enormous hull, potentially larger than an SSBN, making the cost prohibitive.

Making the tender submersible changes the scale of the proposal. It would have to carry enough supplies and support capacity to serve other large submarines. The answer expects a hull larger than an SSBN and rejects the resulting cost. The panel also recalls unsuccessful World War II experiments, without giving a detailed comparison of those vessels.