What I am trying to say is that when you explore you find materials/ores etc… So why not create a RARE mineral that when found affects the soldiers/gatherers and it might give them magical abilities. So for example if someone was ‘changed’ (for lack of a better term) they could gain abilities that use combat types of magic e.g.ignites sword on fire or becomes a full mage and only uses magic in battles (summons ice sword in close combat). They could become a healing unit or they could gain abilites that would help gather either quicker or they could gather a 10x10 area (example only).
Alternately the unit may gain the ability to cause an effect to stay on items (enchanting) but to balance it out enchantments would have to have something to store the energy needed to power it. So an enchantment that makes armour lighter thus nullifying any affect that the weight of the armour causes on the units movement speed. This could be a weak form of a levitation enchantment and this enchant is stored in a crystal(emerald, sapphire, quartz take your pick) that is attached to the armour. This would make some members of your town far more important to protect than others while also providing significant boosts to a small number of elite soldiers. (The enchantments are not straight-up this does that, you have to think a little about which to use).
Also the quality and/or rarity of the crystal chosen affects how the power of the enchantment. For example a low quality/commonly found gem like quartz would not provide as big a boost as a rarer/higher quality gem such as a sapphire. However this system could also be made more complex as a very high quality commonly found gem may provide a bigger boost than a very low quality rare gem. This could all be modded and I know the emphasis that has been placed on modding for this game but I’m not sure I could do it and it has the potential to change the vast majority of magic and its effects in the game.