@MarJamJars#103572 ZeroFX means: when you pay with your Mastercard or Maestro card in a currency other than the Euro, only the Mastercard exchange rate is used and bunq doesn't take any extra fee. It doesn't mean that the Mastercard exchange rate is always the greatest (but most of the time it is pretty good and very close to the interbank exchange rate).
When you use the TransferWise integration to send an international payment, however, ZeroFX doesn't apply. Everything is handled only by TransferWise. And while TransferWise uses very good exchange rates, they do charge a fee for the exchange. (This is a bit different to for example Western Union, where you have exchange fees, but on top of that you have slightly unfavorable exchange rates, which leads to WU earning "double" and calculating the actual fee being quite involved.)
So while TransferWise is indeed very transparent about the fees, and most of the time they're not that high, it's not completely free. After all they also need to pay their staff and fund their operations somehow. And because TransferWise fees can change at any time, recurring payments could indeed be a bit risky. Hey, even if they wouldn't take any fees at all, just the exchange rate for a currency pair varying over time could be a risk in that situation. Maybe you set up a payment for $100 USD and you expect it to take ~90 Euros from your account, but next month the same $100 USD got very expensive and your account is actually debited a lot more.
While the situation is probably not very likely, for some currencies it could definitely happen. So my input on the suggestion would be: Yes, do implement recurring TransferWise payments. But "only" send a push notification and require the user to confirm all the fees and the exchange rate for every single recurring payment. Or maybe only do this when the transaction is at least 5% more expensive than the last one. That way you would have high convenience in most cases, and you'd only need user input if there too much exchange rate fluctuation / TransferWise fee adjustment.