Looks like you're 1 configuration field away from being able to do this - we just need to be able to set the "intent" field to authorize. If you wanted to make it really slick you could provide some sample code in an extension that was a task to re-authorize every 3 days and or to capture payment... See details on paypals developer site:
https://developer.paypal.com/docs/multiparty/checkout/standard/customize/auth-capture/