[HotNifeThruButr]

As far as I can tell, the problem is that

A. Gold/research is always a suitable substitute for resources. The effect is about the same if you, for example, took a handful of resource-heavy Hastati out of your army and put in a gold-heavy Hydra or took a handful of armored soldiers out for a mage that can hurl fireballs/summon monsters.

B. Gold/research has uses beyond the function of resources, which it can already substitute for. You can build fortresses with gold and researched summons are powerful enough to make all troops look like chaff.

From a theoretical point of the view, the only way to fix the scale problem, then, would be to make it so resources has a unique function. This can be done with modding, by manipulating the spell book and the units that may be recruited.

If summoned monsters were less powerful, the "early game" would be effectively extended, since troops would be useful for longer, though this wouldn't make it go on forever, since summons, as a rule, get more powerful while troops do not. The same goes for modding troops to be more powerful.

But those are inelegant solutions that do not solve the problem, only applies shoddy bandaids to it. I would prefer it if Resources were given a whole different function to fulfill that is unique to it and can't be subsituted by gold or research.

What if Resources were directly used to build fortifications instead of or along with money? Perhaps you pay your cash for a castle, but to physically construct it and presumably to arm it with your national weapons, you need resources taken from the province?

Perhaps labs and temples cost resources along with gold?

Perhaps there is some sort of building, maybe an Arsenal that only consumes resources? Perhaps it had a useful and desirable function?