Minetest Game is predominantly enriched by the multiplayer component. Therefore, any feature inclusions will mostly focus on that, as there is zero PVE aspect introduced in the Minetest Game, and mob API support is a long ways off + requires a considerable amount of time, dedication and effort. While I will touch on the ways PVE aspects can be introduced (some form of inherent danger providing a sense of challenge without introducing an entirely new mob system), there is no denying that the multiplayer scene is just as important - one look at the server list and the predominantly used gamemode will support my view.
Player VS Player additions
Feel free to reply with your suggestions and ideas, the endgoal with this is complexity and depth introduced from simple to understand and implement mechanics where applicable.