John Do Outsourcing is obviously the way to go, but what would that mean for the advantage of a one-stop-shop?
Like Rabobank/Interpolis, Knab/Aegon or ING/Nationale Nederlanden you would still have two parties but in both examples the insurance company is owned by the bank (or in the case of Knab, the other way around), so there are mutual interests in providing insurances to bank customers.
An independent insurance company (is such does exists) is sure not to have a benefit compared to direct contracting instead of contracting via bunq. Only the advantage of a one-stop-shop still stands.
But then bunq would have to have more interaction with their customers, or outsource the customer interaction to a bunq branded call center. It would cost a lot and would bring very few benefits.
Let alone the risk this would bring to bunq, a company with very low equity on the balance as far as I can see. That is no problem when you are a bank, but it will be a problem when you start to sell insurances.