Sounds like a plan Steve, however I have one issue...
As all the front lights are now off the same fuse, if that fuse blows, I'm completely in the dark - not a good thing.
Thinking about this further, I'd like to run the switching circuitry (relays and such) off the original wiring, fused from the original 10A fuse in the J-box, and drive relays controlling separately fused circuits off the new, high current (20A) feed off the battery. This would be something akin to a domestic power distribution system, where you have a large main fuse (or circuit breaker these days, of course) to protect the main feed, then smaller fuses to protect the individual circuits.
As a peripheral question, I see in the circuit diagram in the manual a special circuit that is supposed to provide minimum lighting by illuminating the remaining filament in the event that one filament fails. I also see a headlamp bulb failure warning light shown on the schematic. I don't see any evidence of that in my 2006. Am I missing something? Presumably the minimum lighting circuit won't work if there are aux lights installed, as they will draw current and mask the loss of the primary filament.