PayPal has purchased a product called Braintree. It would be great if nopCommerce had an integration with this service. They also list the integrations on their website so it would be good marketing. https://www.braintreepayments.com/features/third-party-integrations
Also, they have an SDK that allows for marketplace payments. In other words, the store owner can set a fee that they collect from a vendor for each sell, while allowing the customer to add multiple items from different vendors in a cart. https://developers.braintreepayments.com/guides/braintree-marketplace/onboarding/dotnet