I seem close but can't quite figure out how to draw an existing panel, in this case "VIEW3D_PT_sculpt_context_menu" in a pie menu.
I can access the menu with
bpy.types.VIEW3D_PT_sculpt_context_menu but cannot follow with .draw() since it is already in a draw context of the pie menu.
Following this answer i can get a colour picker to draw, which seems to say it is possible (:
full pie menu in a pastebin here