If I go with D&D, it would be Basic 5e. Or maaaaybe 2e. Why? FEATS. They bog my group down sooooooooooooo much. - Few people have internalized the feats they have, resulting in constant rule look ups before the players are willing to take their turn. - Few people remember all the feats they've selected so they just use the last three or so they've selected. - Everyone only acts in acordance with the feats they have selected, which limits the actions they are willing to take. So I'm going to take them away. Instead of having players describe the mechanics of the rules that they are taking advantage of, I'd rather they describe the action their character is going to take. I'd rather have to translate player's actions in to house rules on the fly instead of trying to prompt them into roleplaying their character off of their idea of who the character is instead of what they remember about their features list.
The setting I'm working on is already low on player magic. I might go on and make it something that exists in the world, but isn't in the domain of people outside of divine intervention. So while an area might be cursed with a blood rain that turns people into stone and reanimates the dead, they won't be becoming necromancers any time soon. I'm hoping to end up with something akin to Dwarffortress. A grim world where magic exists to grant those that have it terrible power, and a world in which deities walk the earth, but also a world where the common folk are able to hold that at bay through cunning and masterwork craftsmanship. Out of curiosity, how do you feel about non-human races? I was planning on having Dwarves, Elves, Orcs, and Goblins be playable. But now I'm thinking about translating those into simply being different human cultures. (although, which ever route I go, Dwarves are going to sport camelbaks full of vodka)
That actually sounds like an awesome campaign. You should keep me posted with updates and let me know how your players like it. As for non-human races? I LOVE them for everything from variety to bonuses. I especially love when the DM is able to take the concept of various races and incorporate aspects of racism, class and cultural warfare, etc. into the story. Not only does it add more flavor, but if you're able to make you players feel guilty for killing a Gnoll War Party, you're doing something right.