Well, let us think about the basic storyline of this game: the world has been shattered and only few survived. Some few people (or beings) are able to use magic - the channelers. The channelers started their factions and want to save/conquer the world. So:
1) the player itself can research new spells, because he/she can cast it
2) there may be a channeler (hero), that joins your cause and can help you to research spells, because he/she can cast a spells too.
3) general folks are not able to cast spells, so how can they help you? Few may work in some special building (let us say they can search in archives), but generally they can not help you much
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So the point: more mana can help you to research spells. Some tomes, manuscripts and such things from the dungeons may help you to research spells. No farmer can help you, but they may help to research better irrigation system. So the spell research shall remain separated form the magical research.
There may be some positive effect of the research and magical research: if you have invented irrgiation, your flood spell may work better.
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Note: if you have a hero on your side and it becomes stronger than you are, he/she may start his/hers own faction.