The capacitance of the wire will be a problem. PCI is a 32-bit parallel bus at very high speed. Only a few centimeters of unshielded wire will generate a lot of errors. Isolated wire will work better (tough, probabely also for a couple centimeters) , but find a isolated wire with that many connections :?
Just think of it this way, your parallel port (for printer) is a 8-bit parallel bus and at fairly low speed. Extending this cable beyond a couple of meters tends to give problems... So imagine what a long cable would do to a 32-bit bus running at such high speed.