That would be quite a play. Stripe, PayPal, Venmo, Braintree, Xoom all under one umbrella. The Herfindahl-Hirschman Index (HHI) for online card-not-present (CNP) checkout on that is going to be absurdly high and this will take a lot of convincing to beat antitrust. They will probably have to unwind Venmo and Braintree.
If it's a card-not-present transaction, Visa or MasterCard is making the bulk of the commission and forcing the vendor to take on the risk of a transaction without a PIN or password.
At least the others offer the hope that maybe some customers will pay directly from a Stripe/PayPal account, without the high commission and high risk of a Visa/MasterCard network transaction.
Gosh, with such efficiency of operations consumers will win because pricing of their services will be more efficient! Todays Feds will try selling that story.
Convince who? There is no such thing as antitrust anymore in the USA, it’s merely the size of the bribe required to let the merger go through now