Ships of the same Faction, Size, and Hull should be able to upgrade to different ship designs

Yes, i hunger for ability to swap design blueprints for already existing ships of the same hull.

I need to disagree on that. Think of it from a manufacturing perspective. Let's say you make a hull type and make it into a defender. You will have put certain special work in place for it to be a defender. Now comes someone who wants the same ship remodeled as a supporter. You ask why not just create a different ship?

I mean it adds some strategic planning to ship layouts. I would keep it as is.