I know this is quite a late suggestion, but working on new, custom events for the game has made me think of something: is it currently possible to create custom concert scenarios using the game's modding tool? You know, the ones that pop up during concerts, like an idol's heel being broken or the camera being shaky, that sort of scenario. In case creating those isn't possible at the moment, it would be pretty cool if there was a way for players to create those.
Other than that, I'm just rooting for a pretty comprehensible modding tool upon launch, along with an equally comprehensible manual. The software as it is right now already does a great job, but having access to more variables to use in our dialogues and events so we could have even more diverse effects with our custom content would be awesome.