If customer chooses "Bank transfer outside Foodomaa" payment method, they will be taken to running-page with html block as you said, It's okie!
And in dashboard, we can see a sticker telling this order will be paid by "bank transfer", so that admin just wait to receive bank notification before pressing Accept button. And after order accepted, the order is marked as PAID.
In this case (order with "bank transfer" payment method) , store owner doesn't need to press Accept, they can still click Cancel if they can't cook for this order!
About store owner, they just wait to see PAID sticker to process this order to the next step.
About delivery app, the money is counted as other card payment method.