You would probably have to multiplex the amplifier configurations and gains instead of designing an universal amplifier! Also various sources would have different ranges and hence different gains. Michael Karas's idea of using digital pots would be a good way to go.

Don't have much practical experience in signal conditioning, so can't really comment in detail, but they seem to be sufficiently different to warrant different configurations altogether. For example (correct me if I am wrong), the 4-20 mA CURRENT input would need to be converted to VOLTAGE before being measured by the ADC, right? So you'd probably need a I/V cct before your "universal amp". Normally you could have done both with a single op-amp.

kundi