In post #15 and #16 of this thread has somethings I wrote about the install, maybe helpful. You can access the wire connectors without removing the tank or fairings.
I ordered my DX early last year, received it just before winter, and the accessories that I ordered with it did not show up till winter. Given that they sat all winter, and I just got them on last weekend. Off-road pkg rally pkg heated grips utility bar center stand (still has not arrived) I...
www.desertxforum.com
And yes, the three accessories are "dealer activated." I just had my dealer do all of them at the same time. Did do some thinking on why they made it this way, well other than Ducati's fetish with dealer work.
The aux tank, if activated, will show an empty tank symbol, in yellow no less, when the tank is empty. I assume those who do not run the tank would gripe having a yellow light on for "no reason". An easy way out to make a simpler system, instead of a smarter system.
The aux lights, the wires are really small and could easily be overloaded with aftermarket lights. Keeping this locked out is a way for the dealer to get a chance to inspect what you have done. As you, I used the aux light power as a signal to a relay, but not all would go this proper route.
With the grips, this one I'm kind'a stuck on, because the icon is not intrusive and would actually work as a reminder of what the owner does not have prompting the extra expenditure. In the end I think I've settled on the same reasoning as the lights, they don't want someone to overload the factory wiring with aftermarket parts and then take their actions out on Ducati.