I see Maxis is not inspired about city events and notifications become annoying so I propose to let the players create their own city events whenever they want.

For example the players could organize a Sims Session event, set the music genre/lot and the musicians/DJs who will play on stage.

A new City Event venue could be added with 4 templates like Community Space lot (EP09 Eco Lifestyle), the players could select the template to use for the event.