just a thought !
for going through the "only alu" re-discovery by geographs:
there is (was) a number so that mines currently used by the player can discover (1/1000 or 1/10000) a bit of : gem-copper-iron-alu-coal-uranium (me-think)
in genetic era with consummable ressources there is the problem that geographs mostly find aluminium.. but if you just rise the occurence of finding new mineral in mines, you will have appearance of some expendable ressources more quickly than in vanilla game, therfore (with luck) replacing the one that are consummed constructing units and buildings. (it doesn't uses the geograph unit but nothing's perfect)
the only default is that you can only build standard mines in hills ...so no extra iron will appear in plains... so maybe those ressources have a chance of being discovered on in-use mines, workshop : an incentive for using workshop ? or farms ; guess the number of minerals found while plowing a field !!
another idea for genetic era :
(may be interesting even without doign the first one)
I allways thought dumb that crops ressources does not move.
there wasn't any horses nor cows, pigs or weat in the americas, no potatoes nor orange or silk in europe, nor wine and sheeps anywhere save europe and middle east. But now, people can cultivate/breed most of those in modern countries : farmers have moved their crops/beasts with them.
why not create a parameter of the same kind as the one for mines, making that in-use farms have a 1/X (X=1000 or 10000 or 50000000000) chance of "sprouting" one of the crops(animals or luxury ressource) that are possessed in your empire culture zone: any ressource tended with corral, farm or plantation. (such as silk, banana, corn, sheep...etc, but
not furs, elephant, clams)
and maybe crops can appear also when the ressouce comes from trade (not for animals, incense, wine, silk..etc as those travel mostly as finished products and thus not-breedable nor growable .. try to breed silk worms with a roll of good silk !! or breed pigs with some ham!)
something like : 'farms under use by a city have a 1/X chance of specializing into cultivating a ressource'
with a message like 'a farmer near blabla-city decided to convert to sheep-breeding' or 'a farmer near YYY-city decided to grow corn"
and hop! you have a new corn with already a farm or a sheep with a farm on.. you'll have to build a corral though.
it might be fun if a floodpains transforms itself in an incense, loosing the floodplain ability
you can maybe have a verification so that ressources can only appear with this system if the condition are the same as for there original creation (latitude, terrain type..etc : no rice or sugar on plain) (be careful of terrain type: dye needs jungle to be created during map creation, in the case we are speaking of, it should be the green plain (don't remember it's name) in this or that latitude)
if it is unclear, please pm me.
(and no, I'm not the modder type so I have no idea how to do this save that it exist for mines and that 'kael' in FFH2 have created (methink) a mine that doubles or decuplate the probability of discovering minerals in in-use mines so I think it can be doable)
I can build commando too, I think that at least commando should remove those older units from build list
