What should I take into account about the cable

I’ve been working on a homebrew set of VR Goggles w/ head tracking, and am just beginning to plan the cable that will connect the parts on the user’s head to the electronics on the main unit (which will be mounted under & behind the seat the user will be seated in) I’m expecting about a 4ft cable run between the two units, and the connection will need somewhere between 6 and 10 wires (depending on how many ground wires I share):

Manditory wires:

+12v for the video display in the goggles
GND
I2C SDA (3.3v)
I2C SCL (3.3v)
Composite Video
Mono Audio Optional wires:
+3.3V for the headtracker sensors (Could be obviated with an LDO regulator from the 12v
GND (paired with +3.3v)
GND (Video-)
GND (Audio-)
Other requirements:

the cable needs to be flexible, light weight, and possibly coiled to handle head movement without discomfort or tangling.
the cable needs to be commodity (this is a personal project)
the cable needs to be reliably disconnectable/reconnectable
I think I understand the various factors in play (crosstalk, emf, capacitance, etc.) but I don’t have any perspective on their importance for a 4ft cable run.

My back-of-napkin guess would be to use an ethernet cable (CAT 5), wired like this: Pair 1: Audio+/- Pair 2: Video+/- Pair 3: I2C SDA/SCL Pair 4: Power +12V/GND

(Use an LDO for the 3.3v on the sensors:http://www.kynix.com/Product/Cate/231.html)

Is this sensible? What factors should I be most concerned with? Which signals will be most impacted by connectors and wiring choices?