Can the outputs of a semiconductor SPDT-switch be used as inputs if I reverse the switch? I can't see why it shouldn't work, but I though I'd ask anyway.
You don't mention which chip you are referring to, but in general a CMOS switch (CD4066 etc.) is bi-directional. The only requirement is that both voltages (input and output) are within the allowed range (in general 'within the power supply range', where the power pins can be separate from the ground and logic power.)