Please avoid the Civ 4 stupidity where no oil means no tank, no iron means no knight and so on... There is ALWAYS away to make tanks, knights and so on without oil or iron, it is just wayyyy harder and more expensive. For example, coal : you can make coal by burning wood or mining. And there is oil almost everywhere on earth, it is not because Saudi arabia has by far the largest oil stock on earth that others can't drill !
IUn fact if you don't have iron you can build things, but it will take considerably more time. Each point of resources you don't have will cost you 1 turn.
For instance a watchtower wich cost : 15 workforce and 16 lumber will take 36 turns if you don't have any lumber, but it will take 15 turns if youhave 16 lumber available.
Utmost rubbish. If the rules are to go for sanity and realism (chess are a fine game despite that if we (quite shallow) look into the rook's origins then teleporting tower looks somewhat queer) then it must be noted that if you have no wood whatsoever at your disposal - cant trade, loot, whatever else - then darn me if you can build the WOODEN watch tower without use of something like "summon tree" dimensional magic spell. You'll have to build it from stone, or mud, or even consider what for you do really need a watchtower amidst the steppes or high peaks.
A little discource on knights - if to think a little about that full plate armor suit you shall notice that it is darn heavy when assembled from refined steel. No iron means to go for what? Bronze? Which is a LOT heavier and softer, annulling the very purpose of plate armor in addition to making it simply unbearable? Mithral? Considering that knights are only effective in large waves, few scores minimum, you'll have to have a pair of Khazad Dums to field a considerable force.
Same goes for tanks and refined high grade petroleum or diesel fuel, both from oil. You can of course tinker with bio-fuel replacements, steam engines, propane, fusion reactors, suspensors and whatever BUT to get the mass production of tanks at the same tech level and scale as it was in WW2 you will need oil OR produce LESS (not [only] slower, less) tanks of inferior quality (engine power ratio affects not only max speed, but also range and overall weight and maneurability...) OR switch to something alternate or discard tank concept entirely.
The very invention of a new military stuff is based on readily and abundantly available resources, for the cases "we may conquer them with tank armadas, to get oil source that only them posess, so first we buy from them xxx barrels and pray that be enough" or "heck, such periodic element does not exists!" are all too obvious. Defeat of Germany and Japan was largely due to that both these countries were choking on oil and some other (dont rememner whole list) stuff and were forced to go for substitutes - the fabled shale plants and Fischer-Tropsch Process - with poor and insufficient results.
SO:
To freely use a fully functional, generic 'specific resource'-based units you have to possess a sufficient for construction/maintenance input (production/import) and/or stockpiles of resource in question,
ELSE:
- if you do not possess resource stock equal to build cost multiplier you CANNOT produce those units;
- as an alternative you can acquire them from those who can thru trade tribute loot whatever, res still needed for maint;
- if resource becomes insufficient for supply/maintenance these units should be penalized or disabled;
OR:
- you can go for substitutes or alternative similar designs, resulting in inferior quality/penalties (a simple logic: if that resource is military used then it is the best on overall)
- you can discard that unit concept entirely and go for different tech path (as knights vs horse archers - palestina sand contains some good measure of crusader particles)
Civ res stuff was stupid as the whole civ because the moment you lost access you also lost production possibility stockpiles ignored and you was not able to BUILD tanks without oil but still was able to USE them, hilarious reverse.
Oh, btw but close related, units shall take penalties in unfamiliar environments if theyre aint alreday.
About blindly copying medieval units into game: the whole path of European tech development have gone that way because of at some point the Christian clergy had developed their nefarious anti-magic fields. You haven't seen what hasted jerk with knife can do to knight in plate armor or with archers... And haste is not nearly close to most nasty... Play SWTFU to get a glimpse)))
