*Edit* This tool would have different functionality than the existing sculpt mode of the Pencil tool.
My suggestion for the Affinity Designer apps would be to add a tool along the lines of the flash selection tool. Attached below is an example of what it would functionally be able to do: Basically adjust lines/shapes without the need to select them first. It is a quality of life feature missing in almost EVERY vector illustration tool, but flash. It is a shame really. Even illustrator doesn't take advantage of this idea that lives within it's own ecosystem.
This tool in Flash feels a lot like sculpting!
-ability to manipulate segments and points of a vector line without selecting the object.
(this also means editing separate objects is super fast)
-When manipulating line segments, it does not adjust adjacent segments.
(allowing the person to free-form manipulate shapes, and adjust points and segments as they see fit.)
-context switches to a selection marquee when outside a certain threshold of a point or line segment. This selection marquee would add points where it intersects lines and allow the user to delete the selected segment(s), or keep the additional points in their current vector line.
Let me know what you think!