The prohibition against making two attacks in the same action would still apply. Now, if you could manage to load the bolt without touching it (since contact preparations go off regardless of who the next living being to touch it is) then in your example, I'd say you would have to make the crossbow attack roll as normal to hit the target, but you wouldn't get to do damage with the crossbow. If it hit, then you make the spellcasting test to see if the spell takes effect, and so on.
Honestly, though? I'd still be against it, for a couple reasons. First, adepts in general don't need much in the way of help. They can pretty fragging awesome at the things they do. Second, a real low-tech NAN adept would go with a bow, not a crossbow, since that's what his ancestors used. And you can get nasty things already with a bow adept. Third, that's like saying "Bob wanted to play a mundane human who doesn't use guns or ware, so let's give him a little something so he doesn't feel bad". One of the things this edition is big on (and that I really agree with) is that choices have consequences. That low-tech NAN adept CHOSE to play that way, so he should suffer the consequences for doing that. Not saying to go out of your way to make his life hell, but contorting the rules into easily broken shapes so he doesn't feel like he's failed at life is just out. You're right that a crossbow is an inferior weapon to guns for most people. But if you choose to go that route, then it is your own damn fault that you're inferior to the guy with the assault rifle, and I don't feel sorry for you, end of story.