I happened to have tried this before a long time ago before IZ were nerfed, but it should be more or less the same. It works best with Aztecs. Warmonger all game as usual, take luxuries for the bonus attack. With even +4 or so after conquering your neighboring civ, you can guard any barb camp for a long time. You engage/damage the spearman guarding it so it has less chance to riot with a ton of horses. Once you have a ton of camps attacked (and left uncleared) you guard them with a fortified scout preferably on a hill. The warriors that come out of the camp will attack it and will lose 1v1. You get a steady stream of 1xp this way, which is a nice perk but most important reason to do this is to prevent them from pillaging your cities as per usual.
Conquer as usual with your eagles and archers into eagles and crossbows. Nothing really different. Your cities with smaller production that you're not using for real constructions, you can spam scouts. The abundance of scouts serve 3 main purposes. 1. keeping fog of war clear so you don't get barb surprises, 2. Main army combat support. When you're sieging a city, they can provide zone of control to prevent healing. Once enemies have walls, they tank shots from the walls. AI cities prioritize scouts over your real units, so you can move 1 scout in to take a shot, then back out and heal while another one moves into range to tank a shot. Meanwhile your ranged units take potshots with no return fire. 3. civil service amenity garrisoning when it comes along, and a distant 4th, walling off enemy religious units from waltzing through. It's no different from a regular domination game though, since the real lifting is still done by eagles, ranged, and catapults. The moment you upgrade rifling you don't even need to be level 3 to be a threat. Rangers with luxury attack bonus can hold their own pretty easily, especially if you corps them up. They'll all level up easily once you start using them to fight civs instead of barbs. Or others have said, you can leave one of the more useless city states unconquered and farm it for xp, although its not necessary. Id rather have the city for culture/science snowballing.
I'd say level 2 is more powerful than level 3 honestly. The AI prioritizes recon units pretty hard, so they walk up to you. You can easily kite any melee units indefinitely if there are enough hills. It plays out kinda like a budget version of a Russia game doing a Cossack timing window, less powerful in all ways. But I do understand why you would want to do it since I did the same thing before. It's kinda like when you played starcraft 1 against one of your noobier friends and you decide you won't do standard macro map control, you go for a scout corsair rush or something because he's just that bad at the game and it wouldn't be fair otherwise.
The only major difference from a regular domination game is the abundance of cheap scouts being spammed and scattered all over the place in the midgame, and the 4 perks listed above. They cost little to build and have no upkeep. And obviously, you don't ever actually build any rangers using production; you upgrade the scouts scattered all over the place. Each one you upgrade at discount is actually a huge profit for you in terms of production to gold ratio. Still not that efficient overall with this profit, but you don't care about that. You wanna go mass rangers. I feel you
The game settings I used for my mass rangers game was on marathon, deity, pangaea, huge, and it did turn out to be fun, but not any harder than a regular domination game. Like I said, the hard work is really done before rifling by your usual army composition. Rifling is really late in the tree. Oh and I also slid some other bars I don't usually bother with. That game was terrain age: new, resources: abundant, wet, and starting condition I left standard.
GLHF ^.^ manner game plz
