I'm also interested since I'm considering a 2500, which doesn't have the option of cooled seats and I love the cooled seats in my 09 LTZ.
I think it would be pretty difficult. You'd have to swap out the door controls, then run a wire from the door to the fuse box. Hopefully the space for it is there in the non-cooled seat equipped vehicles, but I don't know for sure. Then you'd have to swap out the seats themselves since the cooled seats are perforated and have a slightly different design, and run the wires underneath the carpet to the seat, reattach the power and heat stuff.
See, I don't really know how the cooled seats work (and hopefully someone with more experience can chime in and answer), but here's what I think. I think they have their own fan below the seat that takes air from an A/C duct underneath the seat and distributes it to the perforations. If that's correct, running that A/C duct would probably be the most difficult part.
One of these days I'll take a flashlight and try to look underneath my seats for more clues.
Anyway, subscribed.