So the easiest thing to do would be to not use established characters, but we could easily create a ‘game’ where either all of the players play humans, or all of the players play lesser witches. This is why I don’t think dnd would work because it’s very combat focused, and I’m not sure how interesting an 07th game focusing around combat would be as opposed to using a system which is more fiction-first. In Blades you use the exact same mechanics for stabbing someone as you do casting a magic attack at them or arguing with them.
Blades uses a mechanic called ‘effect’ to judge how much your action does in the game, the more scale/better equipment/more knowledge you have the better you are at doing what you want. So in the 07th example if a human player tries to punch a witch in the face it’s not going to have any effect, but a magical attack or a regular attack with preparation might have some. If we are wanting to have a mix of human and witch players we’d just have to agree beforehand that the witches are nigh invulnerable (because thematically that makes sense). Strange idea I know, but I feel like we’d all be disappointed if the witches in When They Cry weren’t overpowered
Of course the other thing we could do is roleplay witches who also control a piece on the board. That might get a little confusing though.