They don't use WT for Sierra anymore, if it has no letters (other than HD), it means base trim.
As for remote start not being standard, blame the tree huggers, I guess. Some areas have by-laws that discourage running them.
My vote would be to ask the dealer if they can add the factory system, and only go aftermarket if they can't.
Did you install seat heaters? If so, what fuse locations did you use? I have a regular cab, and both left and right "heated seat" fuses are in the drivers side panel. Strange decision.
No recall.
No cost to you for them to apply the service bulletin.
It is an improvement; in fact I get high beamed by road ragers a fair amount, especially other full size trucks. But people have said the upgraded bulbs wear out quickly, and are expensive to replace. That said, I've had them on since the fall, and they're still going strong.
When I bought my truck, they mentioned it would be a good idea to lock the tailgate, or it would likely be stolen. Haven't been bothered to add a power lock, though. Yet.