OSSD

I have only seen OSSD on sensors built for factory automation, but if you do find a device that is also robust enough for use in mobile machinery, I think it could work. 

When the device that creates the output manage the short circuit error detection, the IQAN controller should be able to use it, but it will require extra attention to your application logic to make the input diagnostics tolerate the signal changes.

For diagnostics, it should just be a matter of setting the delay-on time on the DDC you use for cross monitoring.

For the redundant signal, adding an in-between IDC with delay-off for each DIN channel could work. Do consider that this will impact the reaction time for the function.