I have a marketplace app (my users are sellers that charge their users). I love Stripe, but not all of my users do. The number one feature request I get is for them to be able to use PayPal to charge their users.
Paypal has recently launched a marketplace capability similar to Stripe:
https://developer.paypal.com/docs/marketplaces/pp4mp/
A plugin for PayPal that allows me to sign up users as sellers would be amazing.