What does everyone else think about Sulfur being in the game? I'm okay with it, but I've heard concerns that it might not really be rare enough to be considered a strategic resource.
I don't think it makes historic or gameplay sense.
An inability to make enough gunpowder due to resource limitations was never a historic factor.
The whole point about firearms was that they were easy to mass-produce and provide to a large army who could use them without too much training.
I would heavily lean against gunpowder units needing a map-based strategic resource.
Particularly since the existing game design has Muskets *weaker* than longswords, but cheaper and with no resource requirement.
Factions who knew how to make gunpowder could make the gunpowder they wanted; cost was the limiting factor (and manpower), not land-based resources. People never went to war to take their neighbor's sulphur (but they *did* steal their neighbor's horses and try to conquer their coal, oil, etc.).
Horses & Iron & Oil (Opep tricks included!) aren't that hard to come by already -- in reality too.
And thats a gameplay problem. These things need to be valuable, and they're only valuable if they're scarce. We also want policies like Fascism and the Arabian UA to actually be powerful.
Its not I think that we need fewer horse and iron resources and such, but that we should have each version only provide 2 copies.
diversification of assets should compound proportionally.
I don't understand what you mean here.
I think the way to represent increasing access is that eventually resources are no longer strategic.
For example, iron might be rare in classical and medieval ages, but beyond that iron is common enough that units don't need a strategic iron resource anymore, even if they're made of iron and steel.
In a similar manner, late industrial and early modern units require oil, but eventually oil is common enough that units don't require the oil, and instead oil is strategic only for civilian purposes (eg supporting Superhighways buildings).
Hardwood timber stands might be valuable and needed for some early (maybe for the early exploration units?) but wouldn't be needed for 18th-19th century wooden ships.
MEDECINE effect.?.. fairly simple in fact; as of now Production to Wealth or Research are available. 25% Gold (Commerce Yield, as you put it) to Food has similar functions & impacts.
Food should just be food.
Don't mix food and gold together, or food and production, or you get messed up cities that start starving as soon as you stop converting things into food.
Food is different from other resources, because it isn't just an income yield, most food is required to maintain existing population levels.
Medicine should increase population growth rates by allowing a hospital building, like in the current vanilla Civ5 - it reduces the amount of excess food needed for the next population level. That mechanic works fine as is.