Airbags will cause problems with an overloaded vehicle, for sure.
The problem with the airbags stems from where they are located. The area of the chassis around the leaf spring mounts is reinforced and designed to take the maximum weight of the vehicle even on rugged terrain. The area of the chassis where the airbags make contact is not reinforced.
The incidents we've seen (not just in the Navara community) with broken chassis all relate to overloading. If you're going to do things right you probably don't have a worry at all.
For me, I have the choice between airbags and
triple action springs. I'm going to get the springs - because I don't want to risk the chassis at all, even if the Firestone air bags come with a larger plate spreading the airbag contact across a larger portion of the chassis.
It's an extreme that causes the failure. You could probably safely use the airbags as long as you use them per the manual - no overloading, reduce pressure with a reduced load etc etc.
Airbags do compromise your suspension travel for off-roading as well (flex is reduced). This may cause other issues - but if you don't go off-road a lot, that won't be a big deal.
Treated well I don't think the air bags would be a huge drama, but personally I won't go that way.
As for lifts - I can't help yet, I'm not putting a lift in mine. I am torn between Bilstein shocks and OME Nitrocharger Sports - still undecided which way to go with those. Dobinson shocks were (according to the salesperson) not as good as Bilsteins (but better than Tough Dog). I am unsure how much of that advice is retail margin influenced!
