Can I force currents or voltages beyond 1A or 200V using the Keysight 4155A/B/C and Keysight 4156A/B/C?

Yes you can by adding an external power supply. You only need a simple front panel setup file. The best applications are for IV family of curves in the 10 Amp range and moderate voltages (under 40V). In these cases, we recommend that you use the voltage pulse mode the SMU to analog program the power supply. This eliminates heating errors and produces repeatable and precise IV sweeps.You can also click on the 383KB PDF file below to view Keysight 4155/56 application note #5, Measurement of Power Devices Using External Power Supply.