Thanks for the thoughts, guys. I've done several NMO mounts in various vehicles, but I've never seen a headliner with so much crap winding back and forth through it. Thanks, emt.micah, it's good to know that it can be done.
The dome light is actually all the way to the rear, and there are no "portals" directly overhead or near where I would need to drill the hole. The closest breech of the headliner is two speakers almost directly behind the driver and passenger heads (ie, not centered). I did pull the outside cab light, and while it gave me some access, the sharp up angle of the headliner there makes it impossible to get a hand up there without completely dropping the rear part of the liner, which will require pulling apart all of the previously mentioned airbag systems in the columns.
I'm going to poke around and see if I can find some diagrams about the double roof arrangement...that may make or break the whole thing.
I'll snap a few pictures tomorrow once it's light out again, so you can see what I'm working with. I've got a call in to a commercial install tech, and he's supposed to be calling me back tomorrow. If he has experience with the recent model Ram's, I'll probably just pay him to do it.