Your suspension is going to depend entirely on how you drive, how good of a ride you want, your budget, if you are willing-able-equipped to do work yourself, and availability of parts. I have ridden in some wild rigs suspended by serious King suspension, and I have to say that you have no idea what the American West is like. Mountains, forest, rocks, whoops, ruts, washboard, dead-smooth. The testing locations for almost all Trophy Trucks are both 1.5 hours and 4 hours from me right now. I have gone 90mph through 3-foot whoops out here. The race trucks out here go faster. Also, it would be a good idea to take this question away from this forum and talk to an Engineer at King and an Engineer at OME. Those really will be the two best choices, you are on track there. Either way for sure, get new springs as more suspension travel will really help your ride and will save your shocks from having to work so hard. I know that King has a European office, and they do rally raid support in addition to all the racing they do here in the US, they are out there like anyone else.
For sure, as was stated earlier, if you are looking at a lot of rutted roads, you need a serious shock or you need to go slow. I had an Engineer from King Shocks ride in my truck with me last weekend to set up my suspension. I have a 2011 Ram Power Wagon, an American 3/4-ton truck that grosses 7500lbs currently. I have Bilstein 5100's currently, and blow through their valving right off the bat off road. They are way too soft. I also heat them to the point you cannot touch them well within 5 minutes of driving on a trail. We have to go a minimum of King 2.5 with reservoir to get enough oil volume and heat dissipation for this rig. I have driven my friends FJ Cruiser quite a bit and know that they are much lighter, but are still a moderately heavy rig for their size. If you want to be able to drive at a moderate and safe pace over rutted roads, you need a real shock. Those Nitrochargers are either a monotube or twin-tube design and are not going to have nearly enough volume to soak up the heat - their initial valving is going to be long gone within 10 minutes on a rough road, and you are going to be hitting bump stops. If those Nitrochargers do not have an internal floating piston (I have never seen a monotube or twin-tube shock that does), you will lose your valving immediately when you get going fast or hard, even on washboard, as the internal nitrogen charge mixes with the oil and cavitates, dropping the viscosity passing through the valving by quite a bit.
On the availability and survivability side: When a reservoir shock goes bad, what happens is that the oil leaks past the shaft seal. Having a reservoir and a gas charge separated by a floating internal piston means that you lose oil only, not your nitrogen charge. Having the large diameter shock and reservoir means you can lose a lot of oil before you have to fix it. This gives you time to prepare for repairs. You can also rebuild these shocks, even on the trail, so long as you can get them out which is the harder part since you have coilovers. You need a clean environment. You can carry new shaft seals and replacement fork oil with you. Lifespan of the shocks will depend heavily on how hard you run them.
With a monotube or twin-tube shock, when the shock starts going bad you have time to catch it as well, but a lot of the time it goes bad without showing an oil leak, or much of one anyway. When these go bad, throw them in the trash and replace them. The advantage to these shocks is that if you get a bad stone strike on the shaft, you just buy a new one. On the reservoir shocks, you are putting a new shaft in. Cost-wise the new shaft is actually just a little more than what a new monotube shock is, so it's not a big deal.
One big advantage of reservoir shocks that isn't used often is the nitrogen pressure. You can change the ride quality of your shock a lot by just adjusting the nitrogen pressure inside. Obviously you won't do this out in the boonies, but you can use it as a method to fine tune your suspension before heading out on your travels. If you want as well, you can add Internal Bypass and compression adjusters if you get King, Fox or Bilstein reservoir shocks.
There is more to say but my brain is turning off. I hope this helped

Let me know if you have questions or ideas.
Marcus