On a last note, I really don't want weapon upgrades for riflemen considering this is the RIFLE COMPANY. Not CARBINE COMPANY, SMG COMPANY, or MARKSMAN RIFLE COMPANY.
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It should be noted that in US Army Infantry units (and Marine ones for that matter) the term Rifle Company is used to refer to the standard type of Company in an Infantry Battalion. This is opposed to a Weapons Company or a Headquarters Company within the Infantry Battalion. (There is no such thing as an “Infantry Company” as a company of Infantry would in fact be a Rifle Company.)
My point is that while the other USF doctrines provide something unique to them with added flavor or specialized units or equipment, in order to stay “on theme” as being a true Rifle Company, the in game doctrine should focus on the core units of the faction. Adding units or upgrades or abilities is fine as long as they don’t radically change the way the faction is played or your build order. Easy Eights are a great example of this. They don’t change the USF composition greatly, they just give the USF a better general purpose medium tank. This is also why I think the Veteran Sergeant concept fits Rifle Company so well, it’s a general purpose upgrade to your general purpose core Rifleman squads that wouldn’t change how you play them in any drastic way, it just makes them a little better. Heavy tanks, elite infantry, specialized upgrades (like M1919A6s) or heavy artillery are things that don’t fit the theme of Rifle Company.
Going Rifle Company should be like picking a doctrine that feels very plain and general purpose as a faction, but to make it a viable choice it should also be a Good general purpose choice. No real weaknesses, but no major advantage. Easy Eights are just good medium tanks, not heavy tanks. Veteran Sergeant upgraded Riflemen would be just good core infantry, not elite infantry. Flamethrowers on Rear Echelon troops are just basic builder units with a flamethrower like, but not elite assault troops. Riflemen field defenses give you sand bags and mines that some other factions get without a doctrine at all. Rifle Company, the USF Jack of all Trades choice for the discerning Rifleman.