With 6 lights you only need 7 wires up there unless the switches are powered. I had 3 sets of driving lights - I've taken 1 set off so they can go on my bike - I switched the earth, not the positive. Actually, you could still do it with 7 wires with positive switching:
* Positive feed from somewhere under the dash (it's low power anyway so tapping into the cig lighter would be fine, or even stereo power).
* Connect positive feed to ALL centre poles of the switches from the one wire
* Connect negative line for switch illumination from a source in the roof (the screws for the visors would do).
* Connect switch output to your trailer harness, running down the A pillar and through the firewall above the throttle which is below and beside the brake booster in the engine bay.
There is room behind behind the battery for a long panel holding the 6 relays, but you might need an additional relay to use the high beam function. The problem is that high beam is a positive source (that's why I negative-switch, makes it real simple) so the relay won't activate if you feed positive from cabin to pin 85 and positive from high beam to 86. There's a simple way to fix that.
Only for the relays that are going to be high-beam switchable: take a wire from the high beam pin on your right hand headlight and feed it to pin 85 of a 7th relay. Connect pins 86 and 30 to battery negative. Connect all the relays you want to high-beam switch from their pin 86 to this relay's pin 87.
So, the other 6 relays have pin 85 from the trailer wire you've run into the engine bay, pin 86 to the 7th relay in the previous paragraph, pin 30 to positive battery via a fuse and pin 87 to each of the lights.
I would warn you about power consumption. Your alternator is rated at 130A (actually that's for a D40, the D22 is 90A and I don't know what the D23 is but this still applies). That rating is only true when the engine is revving quite hard. At normal cruise (1700-2000rpm) you're making about half or a bit more - say 90A. You need about 30A to run the car (ECU, sensors, other lighting (instruments, parkers, brakes, indicators). Your lighting should not really exceed the remaining capacity of your alternator AND you should limit the length of time you run those lights while idling.
Of course, if you have a set of lights like
these then you really need a standby generator as well.
For those interested (go on, click on the link and be stunned), your car has to be able to deliver 589 amps to those lights (just shy of 300A per light). 300A is enough to give a V8 a crank and will start any 4 cylinder petrol engine with ease. Jumper cables are NOT sufficient. 589A is more power than a winch draws when it's working hard. The average 75Ah starter battery would run those lights for about 8 minutes before it was damaged beyond repair. You might get 10 minutes if the engine was running.
And before anyone jumps the gun and points out that LEDs won't draw that much power so pick an LED light instead - the link is to an eBay sale of a pair of LED driving lights, with 114 individual CREE LEDs rated at 62W each. 114 * 62 * 2 = stupid. Of course, those two lights put my 11,000lumen light bar to shame - they put out 700,000 lumens - enough to light up a football field on their own.
