I have archer line (which is amphibious) and warrior line merge into an offensive infantry line with amph attack starting as early as the early modern period. So longbows and "man at arms" merge into "Shock Troops" which are offensive firearms wielding infantry of the 1500-1700 period. In the west, these were called "Grenadiers" and are trained to throw hand grenades to storm fortifications. By the Napoleonic times (Military Tradition), they upgrade into "Skirmishers" to represent light infantry. By Nationalism they become "Colonial Troops" and by Industrialization they become "Expeditionary Force". By "Rep Parts" they become "Assault Troops" to represent Sturmtruppen type infantry. By WW2 period they become "Marines". By the early cold war period they become "Amphibious Infantry" and by the late cold war/modern period they become "Naval Infantry".
The Shock Troops up to Colonial Troops have a 2-1 atk-def ratio. By Expd. Force to Naval Infantry the ratio becomes 3-2. They're your best attacking option if horses and oil are not available. They hit quite hard and with amph attacks giving a 25% bonus they're a threat. My Naval Infantry costs 120 shields and is 36/24/1 while Composite Armor costs 154 shields and is 48/24/3. Fighting on foot has been heavily buffed with C3X allows units to move after airdrops. With heavy air support foot sloggers can attack and capture ground faster than mechanized forces esp if roads have been destroyed. The helicopter becomes very relevant.
The guerilla line is replaced by Alpine Troops-Mountain Infantry-Ranger-Recon Troops. These light infantry units require no resources to build and have 1-1 atk-def ratio with a low def bombard and 1 movement. But they treat all terrain as roads. Recon Troops are 20/20/1 with 10 def bombard and cost 108 shields. Combine them with helicopters and they can cause some serious mischief behind enemy lines.
Paratroopers retain their very defensive ratio of 1-2. C3X has heavily buffed them. They can now drop without an airport and move right afterwards. At 12/24/1, 110 shields with operation range of 9 they're the closest to stock game. But with armies not be able to pillage they have the niche of airdropping behind enemy lines to pillage or capture high ground. I wanted to give them the rebase function to let them quickly reenforce hotspots but the AI wouldn't know how to properly use it and you'd still be able to rebase when being outside of a city. Still, they have longer range than helicopters and can't be intercepted.
And there's the "Light Infantry". The basic grunt without specialized training. He's cheap and disposable at 90 shields, 20/26/1. But if you need boots on the ground to hold places with heavy defensive bonuses, he's a good option. Many cities can crank out 90 shields in 2 turns with minimal waste.
All foot units can rapidly reenforce overseas territories using helicopter rebasing. While mechanized troops have to use the airlift function or transport ships, resulting in far fewer units arriving within the first turn.
These different types of light infantry distinctions exist in real life because of cost. It would be very expensive to train an infantry man to do it all. Marine grunts aren't trained to paradrop for a reason. And light leg infantry exists because APCs and IFVs aren't cheap. Once the war of attrition drags on you see grunts attacking on foot and riding pick up trucks, golf carts and motorbikes.
With mechanized troops being more expensive (causing lots of waste if the spt is not optimized), the player has more of a reason to train cheaper units and use smart combined arms. The AI too is hurt by them being more expensive (though less so because of their discounts). But they get auto production to make up for it.
Since these units occupy different shield costs, all of them have their niches. I have legit reasons to build them late game rather than just to have fun. They help me win the game faster.
