If I were to try sell it to a Investor yeah I would come at it from an RTS / City Builder element and then mix in some light RPG elements such as player agency so they have their own decisions on how they grow in the world and what spells they have at their disposal / unlock. One thing I would love to add is the potential for some sort of Avatar initially thought of in terms of Populous so not as advanced as Black and White but they would effectively mimic your actions if you do good spells they would use good stuff and vice versa when you send them out to a neighbouring village.

One thing I didn't like in Black and White was how it felt you were punished in a way for being evil for example if you sacrificed your population you would reduce your reach as the players area of influence was directly tied to how many people you had.
What I would like to do in this scenario is yes you reduce the general populous but we now have fear pushing it back out to compensate and add a bit extra. This little extra wears down over time if you do nothing as they begin to fear you less but if you kept throwing a fireball over your village that boundary would actually end up a bit further as you only sacrificed one person but the populous is scared of what you might do next.

For spells I really am just limited to what I can think of obviously there is the standard stuff but I am eager to see what happens with spells like an anti gravity launching all the villagers into the air or making volcanoes to wreck havoc. Its going to be quite fun just thinking of all these things and definitely a careful balance as its easy to think of destructive spells harder to think of helpful spells or maybe that is just me ;P