Yes it is quite a labourious task to do by each individual region.
Each one has a unique combination of six hidden resources that indentify it, this corresponds to the region entry in the descr_regions.txt in the world\maps\base folder.
Taking Sparta as an example:
Code:
recruit "hellenistic infantry spartiateshoplitai" 0 requires factions { greek_cities, } and hidden_resource SW and hidden_resource C and hidden_resource n1 and hidden_resource n2 and hidden_resource y4 and hidden_resource y8
This is from the EDB
Code:
Lakonike
Sparte
greek_cities
Heilotes
244 13 24
copper, iron, sparta, variantgr, SW, C, n1, n2, y4, y8
5
1
and this is the corresponding entry in descr_regions.
So if you want to do it region by region you have to create a new unit recruitment line in the EDB and use the info from relavent region entry in the descr_regions file to fill out the hidden resources section.
This takes quite a bit of work to do so i'd recommend what ISA Gunner suggested and just find another unit with a suitable recruitment range and change the entries to the unit you want.