The round up DD has been suggested a few times but the sweep into JA pot I can see working for people.
Right now you’d have to go through ~14 screens to achieve this manually on each Personal account and of course you’d have to remember too. It’s a bit niche though and I’m not sure that I can see Monzo working on it. What would be great is if IFTTT was extended a bit then this would be achievable as an individual requirement.
If the API allows movement between accounts it could be done on there but I’ve not touched that yet so maybe someone who has could advise?