Multiplayer version of such system would be great ofcourse, however it wouldnt be a deal breaker if only singleplayer is made. For exampple if certain player gets rain and other players only has cloudy sky it wouldnt really ruin the gameplay, unless the rain itself is part of gameplay gather component in large way. If its only considered in regards to visuals then it should be fine. For example if system uses seasons then generally players would have at least similar weather even on multiplayer gameplay. But sure yeh, implementing proper mp version would create more cohesive environment.