Meks If you want to send euro with TransferWise itself you can still pay TransferWise with euro.
So if TransferWise can do this themselves (and make money) it would work the same when it's started from inside the bunq app.
I think the main problem is that the bunq app uses the euro sign to detect if you want to start a transfer with bunq or with TransferWise, so they have to re-think this to allow a euro TransferWise payment.