I like this idea, it would be very handy and also if it saved the subscription ID and then calls the API to check if the payment was received and apply it.
I agree, and I think most of us are coping by just manually applying them and checking the paypal account for payments when a order has been received. (We have the mobile app for PayPal, and it alerts us when a payment has been received which helps allot).
I disagree here, the gateway works fine, it just needs to be adjusted to fit what their customers needs since people don't use the same email address. But again the warning message is handy.