I'm pretty sure the fans are not controlled by the ecu. In all of my ecu disassembly work I have never seen any reference to fans.
One thing I have been thinking about for the future though is re-purposing the post cat O2 sensors. The sensors are only used for catalytic converter efficiency testings, so they aren't really needed. In my own car I have completely removed them and just have the loose connectors sitting in my engine bay. The sensors have an analog voltage input for the sensor, and they have two digital outputs I believe for the heater and amplifier. These could be reused for some other general inputs or outputs.
if only a 0v-5v reference could be used to log widebands like we spoke of earlier. they are 0v-1v though
True, the existing narrow band post cat oxygen sensors are a 0-1v signal. But they should be wired into a general purpose 0-5v input in the A/D of the processor in the ecu. The existing post cat oxygen sensor code in the ecu is only written to read 0-1v, but there is no reason you couldn't read 0-5v if we change the code in the ecu.