https://github.com/exercism/problem-specifications/blob/main/exercises/bank-account/canonical-data.json indicates that this exercise is at least partially intended for practicing concurrency but also that we can implement it without concurrency. However, it's not a terribly interesting exercise in Vimscript without the concurrency aspect, and we already have other exercises that use dictionaries. If you feel differently, we don't have to forego it.
https://github.com/exercism/problem-specifications/blob/main/exercises/bank-account/canonical-data.json indicates that this exercise is at least partially intended for practicing concurrency but also that we can implement it without concurrency. However, it's not a terribly interesting exercise in Vimscript without the concurrency aspect, and we already have other exercises that use dictionaries. If you feel differently, we don't have to forego it.