Will it ever be possible to charge direct debits against Curve, as with PayPal?
No. Curve isn’t a bank account, nor have they got a licence to be a bank, so you’ll not be able to charge direct debits to curve.
You can add your card to PayPal though!
Technically Curve is an e-money account
Monese doesn’t have a license to be a bank either but they support GBP direct debits.
But yeah, it’s not the kind of product Curve is going for.
I believe they’ll be trying to implement a feature for card based subscriptions though where you can remove them from within the app.