This is always a hot topic across Total War: Warhammer boards, and I want to discuss it again with my own bias of course
Having played a lot of Tomb Kings campaigns and SFO campaigns I've grown warm to the idea of factionwide caps, and I think that it is a nice mechanic to be implemented in some way across the whole game.
Many people argue for implementation of Army Caps, because that's how it was in Tabletop Warhammer Fantasy, and these people feel that there should never be conditions for something like 19 Steam Tanks/Dragon Ogre Shaggoths/Star Dragons/etc in one army.
Most suggested idea is that army should be capped by some arbitrary points and a system where you always have to take LL+ some heroes+core+special units.
I do understand why it was great for TT, why it is partially used in Multiplayer already with its heavy restrictions on SEM and other unit types. It provides balance for each player in the individual competitive battle.
But I certainly do not agree that is even remotely good idea to implement it for every race in the game on campaign map, where you intentionally make your positions stronger in one place, while leaving one place less defended, you know, doing strategical decisions.
I mean, for example I'm playing Imrik and have 20 Dragons available through buildings increasing unit caps, why on Earth Imrik would forbid himself to use them all in one glorious Dragon Host (it is even described to be purpose of Imrik in lore)?
Why would not Throt's army really use a terrifying all Moulder-monster stack? Why would not Ikit use his usual Ratling Guns+Jezzail sheningans? Same with other races spamming their elites, really, there is no reason they should not be able to use them all in one army.
I'm all for making some units more rare to acquire, but I'm a firm believer that the Player (or AI for that matter) should be the one to decide how to use these rare units - spread them across all of his armies to make all of his armies stronger, or use them in one mighty fist to crush the opposition and leaving other of it's armies less than ideal in return.
I like Troy's idea of resources making higher tier units harder to acquire with different resources needed to recruit them. I'd also like to see more local recruited units. For example, I find it is too easy right now that you can increase amounts of elite units you can have with each tier 5 province for TK, it quickly leads to switching your skeletons out with tons of constructs.
Maybe factionwide unit caps should be bound on some other factors, like for example Casket of Souls for Tomb Kings or Queen Bess for Vampire Coast. I generally like to see different methods of recruiting new units.
I'd love to hear your opinions and suggestions!