Monthly subscription with Stripe using iDEAL
Have you tried having a look at the API Docs for Stripe? They have written about ideal integration: 

https://stripe.com/docs/sources/ideal

If its in your budget you should probably also have a look at Craft commerce which has partial Mollie integration which should, in turn, facilitate the iDeal payments solution that you are looking for. Though they do say it is only partially supported so you may need to investigate if this is exactly what you are looking for.