Side-by-side schematic symbol view / code view that are actively synced to one-another in real-time. Schematic view allows basic arranging of parts, editing interconnects, triggering jump-to-reference within the code view, adding probe points for SPICE, displaying SPICE output graphs. Code side does all the heavy lifting like creating new parts, scripted behaviors, editing component values, all the cool shit that would be a nightmare to sort into a GUI.

Much easier said than done, of course.