It's an interesting idea and I've worked with organizations that have set up long range Wi-Fi networks. A good example is Air Jaldi who is the main internet provider in Dharamsala, India in the Himalayas. They've based their network on Wi-Fi to provide access to the mountain residents and run one of the world's largest WiFi networks.
There are a couple of things to consider to try and set up a long range Wi-Fi network. First one would be the topology. This is kind of like how wide of an area do you want to cover. You can get distance with highly directional antennas although it would be point-to-point and wouldn't cover much range in between. Some amazing distances have been achieved using this method. I worked with some people from the team at ICTP who set the world WiFi distance record. The conditions are unrealistic though unless you're beaming down from a mountain top to a valley.
For coverage, you'll need to figure out how to distribute connectivity and this could be using hub and spoke, star, or mesh topologies. As a side note, when I was talking to Air Jaldi, they gave up on mesh technologies because they were unreliable. You'll definitely need an array of antennas as well as access points and amplifiers/range extenders.
The big issue is that the assumption of a large WiFi network is that you have access to two critical pieces of infrastructure, reliable internet connectivity and power. If you don't, you will need to build these out yourself which means you'll also need batteries, solar panels, MPPT chargers, and probably inverters. The issue is that if you're working in remote areas, these all get stolen quite easily which means you'll also need to consider security.
I hope I'm not discouraging you from trying. These are the real world issues that you'll probably encounter if you try and set something up in a remote area.
Hope this helps.