By coincidence I was meditating on this exact topic just before visiting the forum, and in fact, I came to the same conclusion that the early 50's HP triangle is the best solution. It's the most intuitive, has positive and negative just as you will find it on an schematic (positive is the uppermost, negative is on the bottom), it has 3/4" spacing between all connectors, you can use 3/4" spaced dual banana plugs as well. Binding posts accept bare wires, U terminals, banana plugs, alligator clips, clips, short bars, actual bananas...