ADC input software multiplexed between current/voltage input
You can switch the load resistor in or out with software using a solid state switch but you have to measure the voltage on the resistor side of the switch (so that the switch resistance does not affect the reading) so you need to multiplex the ADC input between the two. You also would need a PGA to accommodate the 10V voltage input vs. typically 5V (or less) burden from the current input load resistor. Maybe just a 2:1 gain selection which is easy with another 2:1 analog mux. 

Make sure the switch you use is not too high resistance or it will affect the required compliance from the transmitter and take appropriate precautions (beyond the scope of this answer) to harden the inputs against transients etc., such as from long wires and a nearby lightning strike. Properly designed industrial process control equipment has a lot of such considerations included, especially compared to hobbyist open boards like the Pi.  







simulate this circuit &ndash; Schematic created using CircuitLab