Wow! Thanks for this Nate -- that's great news that it's planned for your next release!
I'm developing for Android and iOS (Android first).
Yes, the operation you describe is pretty much what I need. My app uses an escrow, so rather than just [User pays App, End] each customer payment will have numerous subsequent functions, some of which record data (payer and payee record) and other transactions (I.e. [escrow to payee], and/or [refund from escrow to payer]). As well as matching payment records to database records of what was purchased, if it was delivered, by whom, etc.
I understand Dropsource already supports the database table write and call functions through other APIs (correct me if I'm wrong) so I'm sure I will be able to get PayPal payments and functions working as designed once your next release is out.
I'll document what I learn and how I end up doing it too for the wider community. Seems like a widely useful thing to share.