In the way of a Wikipedia for merchant data, so all Fintech banks could contribute back to a open repository of information, and people contribute back to it individually as well (with obvious anti-vandalism), this could stop customers from having to re-enter merchant data again and again across different banks and mean that in the end, all banks have a better source of merchant information. This could potentially save customer services time too as it means less work and duplication for customer services too.
Well i would argue that Merchant data kind is already open source (kind of) - I know Mastercard has a merchant API. Its just very difficult(in my opinion) to use. if anything a spin out of Monzo that just did this would probably be quite profitable assuming other Fintechs use similar technology and legacy banks want a slice.
Here in Portugal we already have something like that. All merchants send data to the government for every transaction so that tax deductions are automatically applied. A lot of credit card companies already use that merchant database to attribute cashback benefits