This is a feature that many other eshops have and till now I do it with custom code.
It is important to have an option to show the bank accounts for the client to use in order to pay. This info will be displayed along with the order details after an order is completed using bank transfer. Clients can't always wait for the email. It is not good to say to the client to change app and check his emails for doing the payment. If he sees the payment instructions in the complete order page, then he can simply copy the account number and proceed to his e-banking app.
Actually a nice idea is for every payment method to have an editor in the parameters in order to add text with special instructions. So we can write other instructions for bank transfer, other instructions for payment on delivery etc.