Dave I do not know if it is possible to get all those functions in a compact box without electronic control circuits. The problem is heat dissipation. A small box would get too hot too fast. In college for my senior project I made something very similar to the Sure Test meter using momentary switches, resistors, and banana test plugs for meter in a utility box (wished I had patented it). I also used a load box to test higher voltages like 240, but at the time I was an intern at a utility company so I was able to use precision “Ohm Spun” resistors from junk equipment. It would be very expensive to buy them on the market.
In order to test CB trip values you need to get resistance down to 1-ohm @ 100 W to test a 20-amp breaker. Granted a 100-watt resistor is not enough wattage for continuos load, but should work for instantaneous trip region of a 20-amp breaker if using a momentary switch rated @ 100-amps.
Another thought would be a bank of light bulbs, but that is not small. Which brings me back to the point I have been rambling on about. I do not think you can cram 10-pounds of poop in a 1-pound box.
