Klaus should read jon.in.ct.home.att.net/SAE970843.PDF to understand the WRX's current A/F sensor or jon.in.ct.home.att.net/SAE2002-01-0474.PDF to understand how the new sensor will be used with 2005 MY Subarus.
I read it. To simulate those kinds of sensors (current limiting single cell) with a wideband controller like the LM-1would require some external circuitry. The conversion from output voltage (as from the LM-1) to constant AFR dependent output current is not difficult. It just requires an op-amp and some resistors to make a voltage to current converter. Then download the desired conversion map. I see the bigger problem in fooling the ECU in the heater circuit. Most ECU's for the more modern sensors also monitor the heater current path and throw a fault condition if the heater circuit is open, because this one indication for a disconnected or faulty sensor. Maybe the ECU in question would be happy with a constant (high wattage) resistor. But I don't know enough about the ECU to tell.