Adding diesel and crewcab will get you close to $50k i bet!
What are the owners not impressed by? Any forums discussing it?
Try this thread, if you can access it:
Also of note: The 2015's had terrible transmission programming. By 2016 it was way better, and most of the 2015's got some of that reprogramming. My Z71 is a 2016 (gasser, not diesel) and I've learned to mostly 'drive around' the one weird spot in the programming. HOWEVER, some guys are already trading their 2016 trucks for 2017's just for the 8 speed transmission. It's THAT much better.
Oh, and if you want a 100 HP boost, Mallett is making supercharger kit for about $7k. Giddyup.
I told myself I'd trade this one in at 8 years max to stay ahead of the rust problems my Highrider suffered from. If the ZR2 package is all sorted out and readily available, I might just move that up to 5 years.