What patterns are people using to switch between different types of game modes, maps, singleplayer vs multiplayer, etc? Have you had more success cleaning up and reusing your simulation worlds, or destroying them and bootstrapping new ones?
Personally I reuse the world and systems and wipe all the entities (except for a few marked as exceptions) on scene change. But I suspect this is generally an unpopular approach because a recent survey told me that was one of the least-used features of my framework.