I noticed the 2500 is the only Avalanche with a snowplow package, I want a 1500 and would like to plow a little with it. But anyway why can't you order a sun roof with the snowplow package on the 2500?
1500 won't take the long term stress of plowing. I know that a lot of people use 1/2 ton trucks for plowing but it eats the tranny alive if it's not set up for it.
With that said the snow plow prep package has all wiriing set up for aux lights. My guess is that wiring in the roof eleiminates the ability to put in a sunroof.
The "snow plow package" only deadheads the wiring for the AUX lights in the "B" pillar - it is the buyers responsibility to connect them so there must be some other reason for the options choices.