I have an RGB LED / LED WIZ project, does it sound manageable?

I have a larger scale version of THIS INSTRUCTABLE, spreading out the led's more, and need some help/advice/comments.

It is pretty much a 120' length that I want lit, with rbg leds spanning across. The led's will be paired(paralleled) in two's, and every other pair will be on a different channel (example: chan1, chan2, chan1, chan2) so I have separate control over every other pair.

For each channel I can have 12 pairs (500ma), each pair uses 3 channels (rgb) and I have 120 pairs, so 30 channels.   I plan to use a computer power supply as a dedicated power supply for this (5v/30amp) to run it.

My questions are these.  First, do you think a 14/4awg running to 12 pairs 120' away would work? Do you think this whole setup will work, and if so, whats the weakest part? Finally, do you think anyone else is crazy enough to spend this much time on it LOL?

This is for a commercial project, so I am really hoping it's manageable. If anyone doesn't understand let me know and I'll draw it out for you.

P.S. If 14/4 wire wouldn't work well at 120', whats the maximum length that it will work for 3.5v/500ma pulling from a 5v/30A source?

you will have a major volt drop with DC and that length of wire
your going to lose over 10% of your voltage at 5 volts easy
1 boost voltage to counter the drop or move closer 

this list is something to think about

1. use a 12v dc setup with get you to that range.
i can wright up a how to wire a LED-wiz to run 5 ~ 24volt range outputs safely at 500ma load ea ch
and how to build add on mosfet amp's to drive as much as 20 amps per channel this is a easy thing to do

2. use 1/4 watt resistors on each color on each and every led
    (if using RGB SMD strip most come setup for common anode for 12v and have the right resistors onboard)

3.all the load feeds on to just that 1 wire

4. remember each color of a RGB LED use's different voltage
red tends to use less 2.0~2.25 volts blue is a odd ball and i have seen
2.5~3.2 volts check the spec on your LEDS green is avg 3.0 ~ 3.2 volts