I was actually hoping they would put in a manpower mechanic in, showing the able populance that can be drafted/levied, and those willing to sign up has professional full time soliders. So kinda like the class system showing what role a certain individual can serve or be allowed to serve in until a reform of such took place, but may be going a bit overboard.
But i would like to have to choose my army composition carefully, making sure i have good mix of native troops to act has the vanguard while using mercs which will reduce the strain on drafting natives from home regions or "AOR" for a higher price & upkeep. The entire populace should not be all recruitable, so with any total games, especially NW, were it is possible to recruit a settlement down to almost 0 - 400 populace or somthing, with each unit/regiment taking up a thousand souls or so?, that the population number stated is the "able fighting populace" Although i would like to believe that should be broken down further to those willing to become professionals, and those who are levied at short notice, much like the battles against Hannibal, but the role was more suited on your class or wealth in what protection you could afrod, compared to the marian reform that increased the supply of manpower at the cost of diluting the cultural make up of there army, with non Romans mostly making up the auxiliary.
ManPower should work alongside culture i think, if a region is made up off 20% Romans, 70% Gauls, that came that should be the recruitble ratio. Until you exhaust one or another, With the use of mercs or foreign cultures more subjective to being bought off by the enemy, or betraying/defecting, hopefully depending on past grievances with its homeland or the current state of affairs and may decide there best interest isn't to fight alongside you. So any expansion made by a player will mean, they will have to exterminate an area, and then allow settlers to reach the new frontier and develop a loyal roman town/economy, or occupy and demand the captured region put on the yoke and serve your nation. Has regions are vanquished/exterminated, a natural amount of the population would have fled to the next region over, I feel this should be shown, and hopefully has a foe is pushed back, will naturally becomes stronger, with more manpower/able bodies and territorial price/war fervour, becoming a war of attrition until one has exhausted its manpower/supply limit over reaching to knock out a foe, or able to deal the death blow. But I think the population should also keep migrating if that the case, such as the fleeing of the Gaul population seeking refuge in Briton and Germania, giving them a manpower boost, economy, and access to loyal mercenary’s.
Also maybe seeing small states pooling there forces together, as the Greeks did, so an option to send/dedicate manpower/supply mercenary’s to another factions war effort.
But tbh, I not to sure why people are asking to make it possible for smaller factions to be playable in the sense winnable, due to lack of “manpower” is asking to much imo, a faction can be small and dense/sparse in population and be able to hold it own, maybe through an alliance, or maybe you should be able to vassal yourself out to a bigger nation for protection until yur ready to throw the yoke off, but having every single one of the 50 nations or more are balanced, your have a stalemate, with no one expanding and no end game, not that I would like to see Gauls and Briton in a war to death, but instead lending help and aid when a bigger threat present it self to there way of existence. Some factions are going to get wiped out..., I think they said, some of the ai behaviour is scripted, factions like Rome & Carthage, and some is based on personalty, which can change I think?, so I don't think every campaign will play out exactly the same.
Some people have made some really good suggestions on how a manpower system could work, the thread is around here somewhere, but I don't think it gonna buff the player into being able to steamroll, instead should reduce the momentum of the player, if troops need to be lost due to attrition while being on the march in certain conditions, losses in battle, sabotage by agents, supply limits being cut, and at the same time, only being able to maintain a population that you can feed, if not, they migrate, riot, defect, and cause further harm to your population total. Has opposed to being a smaller nation, that could vassal its self out , financing other wars to put strains on to a bigger faction until your ready to send physical force yourself.