I think, that if Monzo was serious about helping their customers avoid unexpected fees, then this could certainly be significantly improved, as it’s all very opaque at the moment.
The best option I could think of is a banner on your feed (similar to how services disruptions are shown). The banner could be (1) dismissable (2) only show when your allowance is less than £200 (ie you have mad a foreign withdrawal in the last 30 days) and/or (3) supported by location data (ie only shown when outside the UK).
It could then show “Your current foreign atm allowance is £115. It will increase by a further £80 on 6th June.” (round all figures down to nearest number to aid comprehension.)