Seriously PayPal, get on this. I just asked for the same thing in the comments further down. We've got an international base of clients asking for PayPal support and we're using Stripe. Rather than force us into two flows on our end, work with Stripe so we can just utilize them and you collect $$.
This is awesome, and you are awesome Patrick. Gotta have serious respect when the founder of Stripe, who I have to assume is quite a busy guy, shows up to personally respond to comments, encourage new features, and drop his personal email.
Tough to say. I know that Recurly has gone the approach of supporting any number of gateways (http://recurly.com/gateways/). Is there a technical limitation of Stripe that doesn't allow for this?
I was under the impression PayPal does allow charges with their Direct Payment API (i.e. Payments Pro). Are you specifically referring to the fact you have to be redirected to their site for login to do so?