This has been done before;
A recap;
- Bill Splitting for joint accounts.
- Monzo.me for joint accounts.
- Shared Tabs for joint accounts.
- IFTTT for joint accounts.
- Overdrafts for joint accounts.
- Loans for joint accounts.
There may be even more now, with the new UI and recent feature additions - a couple of removals from the JA spring to mind regarding the new android beta and also viewing external credit card balances;
- Show ‘Your Monzo’ (for my profile) in the joint account profile, which shows ‘me’ anyway
- Show ‘Monzo points’ (for my profile) in the joint account ‘View All’ display
- Allow selected/designated connected Credit Cards to be shown in the joint account ‘View All’ display