Interesting ideas I don't know if the economy system is already set in stone but this could definently help make the reasource managing easier. 

You're assuming that upkeep is linear rather than geometric, that a large empire would have the same average upkeep per unit as a small one, and that efficiency gains through superior placement or technology do not provide sufficient offsets against sprawling empires with less exacting placement.

You additionally make the assumption that it is a bad thing for large empires to be rewarded with units/structures otherwise inaccessible to smaller empires, and that land is the sole source of resource acquisition.

If we reject even one of those assumptions, your conclusion -- that a flow model is overly rewarding of larger nations to the disadvantage of small ones -- does not follow.

Geometric increases in upkeep for each additional resource acquisition structure would tend to disadvantage larger nations by creating a diseconomy of scale. Average upkeep (here used loosely to mean all costs associated with keeping a mobile or stationary unit) could be increased with a "distance to capital" corruption modifier or a population check. Finally, a loss of per unit efficiency due to the greater quantity of assets in a large empire relative to available player attention per turn (a quantity that generally remains reasonably fixed for a given player, but varies widely amongst the population of players) should almost invariably decrease potential gains for bigness, except for the most obsessive of players. 

There is the additional assumption that bigness should not carry a reward distinct from the mere fact of being big. In Civ4, a player who possesses only four cities cannot complete several national and world wonders that require at least five of a specific building. In Magic the Gathering, a player with only two mountains cannot cast a card requiring the mana of three. Neither of these are inherently bad, so long as the player has access to a sufficient number of additional tools that allow them to remain competitive with a smaller than average resource pool. 

As to whether land is the sole source of resource acquisition -- this is a game where nations are ruled by powerful channelers can remake the world at will. I assume that magical acquisition of mundane resources will be possible, either through direct player action or the creation of magically financed structures. A small, magically focused nation could -- were this assumption incorrect -- therefore create a powerful empire irrespective of their negligible geographic footprint.

If you check my OP again, you'll note that I viewed increased fragility as a plus rather than a minus. Stockpiling allows players (including the AI) to disassociate their ability to fight from the reality on the ground -- after all, a player who has stockpiled resources for eleventy billion turns (where eleventy billion is any integer greater than zero) is fairly invulnerable to shocks to their resource acquisition network, and thus to raiding. 

To pull again from Sins of a Solar Empire, in the late game a successful player can, due to stockpiling, typically afford to lose several fleets and planets before they are materially injured in a serious way. With a flow system, a Sins player would be immediately injured, having lost potential capacity. 

As a response to the "use it or lose it" mentality a flow system tends to engender, yes. That's an unstated goal of the system, and a fairly blatant means of signalling the player that they are over or under-investing in resource acquisition -- and unlike in a stockpile system, that feedback on investment is immediate and robust, not dependent on a long period of time and heavy spending beyond their means.

However, I do agree that every system should have at least some give. Therefore, I'd suggest enabling the player to temporarily sacrifice a certain amount of output in any resource or group of resources in order to increase output in another resource, or group of resources, with ratios determined with reference to relevant factors. 

I'm not convinced that there's that much between flow and stockpiling resource models. There are positive and negative examples on both sides. What makes or breaks the system isn't the model, but its implementation (surrounding mechanics, e.g. pay-as-you-go vs.  pay-up-front). I prefer the stockpiling model because it does insulate production from resource control -- although, obviously, there should be limits -- but I'm willing to concede that certain mechanics can be added to a flow system to provide similar insulation.

Just your point of view.

In Kings Bounty you stockpile (collect and get thru advancement of levels) mana, mind and might runes. Then you have to spend them and its very difficult to prioritize. I love such mechanizms

You suck.

That said, you can store most things beside food virtually indefinately, if you preserve it properly. Including wood.

Your population is always the same, never dying of old age and just increasing by a neverending quantity of new people already adult and equally inmune to aging.

One soldier you train in your first turns, if not killed during battle, could survive until the very last turn of the game as it won't die of old age either.

The buildings of your city never need repairs due to the passage of time.

Arable lands can keep producing food non-stop, soil depletion never happening.

I noticed that several people brought up realism claims in favor of stockpiling (stuff can get stored), so I pulled the same (stuff degrades). For rather obvious reasons, neither is a valid argument in a video game, and several other posters have taken the time to point that out.

Systematically ignoring me? Interesting way of putting words in my mouth. I did ask that people respond to some of the specific qualifications I added, but only so that I could modify points in response and further hash out the conceptual backing for the flow system. Please don't bring the drama llama, because then I'd get all troll on you and things would get stupid. Stupider. Whatever. 

Since my goal is to promote an idea (that there is an excellent alternative to the standard resource stockpiling model) rather than comment on a specific gameplay mechanic ("farms should produce a flow, and stone should be stockpiled"), I disagree with you that this is an inappropriate time for this discussion. And, considering the sheer number of replies, and the rapidity with which they have accumulated in comparison to my other Ideas threads, I'm of the opinion that, pro or con, others agree that this is a viable topic for discussion.

Don't you need a permit for that?

I'm willing to concede that, yes, well designed systems compare favorably to poorly designed systems of the same type. However, you failed to include any relevant set of criteria for comparing two equally well crafted, but functionally different, systems. I maintain that, due to the inability of the player to continue endless aggregation of resources, the stockpile system is inferior to the flow system in the middle and late game periods -- periods where the players have a sufficient resource gathering infrastructure to develop titanic stockpiles.

Because the flow system maintains a tight connection between the productive capacity of the player and their ability to purchase over the totality of the game, and because the stockpiling system fails to maintain that same tight connection over the totality of the game, I argue that the flow system is indeed superior.

The game already use a "flow" system. You don't stockpile anything, but gold. Not even mana.

How rude of you to ruin the voyage of discovery for all these fine folks! This was developing into a real page turner!

But, since the jig is up, I guess I should mention that just about every turn based game since Civ1 has used a flow model for building and research -- with the obvious exception of that terrible series known as HoMM. 

In actual build yes, but in the future no. They said that spells will be used like in Magic the gathering. Each spell will need a fixed amount of a particuliar mana shard. For instance a fireball would need to control 1 fire shard.

Maybe they'll add some way to stockpile for next turns or whatever.