You can vote for the upcoming features on the roadmap & hopefully Monzo takes into account the amount of interest that there is in the community (here), for the different features that’re requested.
I suppose most additional features that Monzo’s considering need to be built on top of the foundation that those developments are creating.
Obviously votes on the roadmap are only one of the factors that Monzo will need to consider, as they know their long, long term roadmap, how users are using the app currently etc.