For the Digital Good Marketplace, yes... since the system handles everything, there has to be a way for it to handle payments too. For the old marketplace under the forum, you only need to link PayPal if you want to be able to earn feedback (since it's based on Instant Pay stuff).
But what about if we want to sell something using other payments methods, not only Paypal. For example if I want to sell something via Payza, I sell this product, I receive money, everything was perfect and I want to give a feedback to my customers (or customer want to give feedback to me). If I wasn't paid by Paypal or if he send money directly on my account, not via DigitalPoint, I can give / receive feedback? That's doesn't looks so far, will be nice if you can make other system, to post a proof that you send product and got money (like a screenshot or something), or moderators to check and approve each feedback. I don't know, something like that. There are many users without paypal (there are many countries without paypal), is not fair for them.
Sorry... Not going to happen as far as people "submitting proof" a transaction happen that we have to review.