The air suspension, for what it is, is pretty remarkable. It allows fairly serious offroading, while maintaining the ability to cruise comfortably on the highway.
First, you need to decide how far down the modification pathway you want to go. If you want to exceed 265/65R18 tire size, you should look very hard at adding the Proud Rhino strut spacers. These spacers bring their own set of compromises, but what they will do is allow you to remain mobile in the event of a total suspension failure that drops the truck to the bumpstops. Without these spacers, any tire larger than 265/65 will be crunched into the wheel wells, and you would essentially be immobile.
If running the spacers, you also need to run "lift rods" to keep the air strut pressure within a range close to stock. Without compensating for the 2" difference in strut height, your truck would remain at factory ride height, but with commensurately lower pressure inside the air struts, resulting a crappy ride quality.
Next, consider mods to increase the serviceability of the system. I run and recommend the GOE "Emergency Air Kit". This system allows you to segregate each individual strut in the event of a failure and manually inflate the strut from an alternative air source (on-board compressor, Air bottle, etc). With this system in place, you can compensate for any form of mechanical or electrical suspension failure with the sole exception of an actual ruptured air bag, which is a very rare occurrence.
A GAP tool is almost a must if doing the aforementioned mods to allow you to fine tune the settings after your mechanical changes as well. It can also be extremely useful in troubleshooting or compensating for issues.
If you want 100% reliability if heading into the sticks, consider throwing a spare front/rear strut assembly into your kit. These can be changed trailside if it comes to that. 4 tools, which you should also be carrying, will get the job done.
I would never consider changing to a coil setup. It would compromise what is so great about these trucks. Drive to the mall, or drive up a mountain. Just push the right button to make it happen...