Modularity! The vehicle.

This truck would be designed as follows. The shape is a cylinder, but with reinforcing titanium bars on the outsize forming a square girder. It is symmetrical front to back. Four all-terrain wheels extend outwards and down: one from each corner. Each very well-sprung wheel has an independent electrical motor which is placed on the vehicle at that corner inside the girder. Ground clearance is large. The front and back of the truck each have a docking port.

Docking port: It's a heavily reinforced device for connecting the truck to a truck just like it, such as space-craft use. The differences are: weight is not a particular design concern. It's very robust and resistant to bending. It has a thick rubber-like gasket that can let it act as a seal underwater or while traveling. It includes more than one pump (for redundancy) to push water out from between two connecting vehicles if the vehicle is underwater. It acts as an airlock, in that it can maintain large differences in pressure between outside and inside when docked and independently if it has to act as a hatch. The docking port is designed to hold on and absolutely not let go under enormous forces until it's told to let go. It's also capable of rotating the outside of the docking port while linked so two trucks can rotate relative to each-other or lock to prevent rotation.

The front and back of this truck look the same and the docking ports are androgynous: each can connect to any other.

One truck design may have a kitchen inside. One may have a crew cabin. One may have a motor. One, batteries. Communication equipment, a repair truck holding everything needed. The point is that you should have at least two of each type that you need. The docking ports can transfer air and electricity but water, hydraulic fluid, and the like should be kept unique to each vehicle.

These trucks would connect to each-other in a long road train. It would be able to traverse just about any terrain that can be found, under or over water. Any tank trap, crack in arctic ice, or set of ridges could be driven over by extending the front vehicle or two over using the weight of the back ones. Any vehicle on its side can be connected to and rotated upright. If you add docking ports on each side (or if you're willing to send guys out with ropes) you can even connect them laterally into wider beams for greater strength. Is the crack too wide or the hole too deep for one line? Try four!

On a smaller scale if a motor goes out, a wheel is blown, or a truck becomes otherwise partially disabled it can simply be kept connected to a more capable friend and keep going. If a truck is irrecoverable or no longer can provide its primary purpose it can simply be left behind.

I estimate that a convoy of 20 to 40 of these guys could go anywhere on earth not covered in lava or over two kilometers of water.