Welcome and congrats on a (hopefully) mechanically sound family war wagon!
I don't know what rust is, but it sounds like you've gotten a handle on that with the recommendations from those experienced with it.
There aren't as many options for aftermarket headlight assemblies for the GMCs as there are for the Chevrolets. But, I believe there are all-black housings, where the inside part is black and the headlight is a projector instead of a reflector, so it is more ideal for HIDs.
Painting or wrapping the chrome bits to match the body color and/or making them black goes really well with a gray body and would certainly make it look tough. Gray body, colormatched trim, black wheels, mild front lift to level it with the rear, black or dark gray wheels with all-terrain LT tires... The tough looks would compliment its capability and sturdiness while still looking clean and civilized.
I'm all for the AFM disabling. GM upgraded the AFM components that started with (I think) the 2011 models. Or maybe it was a mid-year 2011 thing. Either way, you won't miss it and I'd still disable it to be on the safe side. However, I'd make it permanent and avoid the other potential issues that a plug-in module may present and have it tuned out. Either get a full custom tune, which would also improve many other aspects of the rig or just have the AFM disabled. You can send your PCM here:
https://lt1swap.com/afm_delete.htm and have it turned off and be done with it for less than half the price of the plug-in module.