One of the most important tools in Rhino is “blend surface” that has remained, more or less, the same in the latest versions.
This tool should be made more robust and complete (I would look at Vsr shape modeling). For example, one shortcoming is continuity management at the ends of the edges. We need more controls. Why not implement them as soon as possible and make this tool really convincing? I wouldn’t want Rhino to focus much solely on subDs while neglecting some fundamental aspects, like this one.