Hello! We are currently focused on improving the new player experience between levels 1-10 so it is unlikely we will be adding a higher difficulty at this time. We will be looking into improving the delta between beginner and intermediate bots though to better cater to new players at those skill levels as right now they feel generally the same.
For custom games, we do not have plans to add any additional bots or unique features for the foreseeable future. Once we have a solid additional set of bots available in Co-op versus AI though, we will go in and add them to Customs. (Currently only Ekko is available in Co-op and unavailable in customs.)