Haven't done it, but do you understand how to use the pairs of CAT5 to minimize interference? That is one potential problem.
The other potential problem is distortion of the waveforms that come out of the controller due to the added capacitance of the added cable. To make this work if it does not, you will need an oscilloscope which you can run without its ground being common with your system and some information.
Email me if you try this and it does not work. i've done the scope thing with an IR emitter that I removed from a remote control and placed 75 feet away. The waveform got messed up but I was able to correct it.
Ernie Bornn-Gilman
[email protected](that LA is Los Angeles, not Louisiansa)