I don't think anybody has a problem plugging in the numbers on the fly...like I said, happens all of the time. What I have a real problem with is telling the tower that we need to stop, set the brakes, and plug them in because somebody in upper management thinks it'll be too much heads down time. As an LA guy who flies to JFK and ATL almost exclusively, DAL will become the most hated airline out there and I'll be biting my tongue every time. It'll be embarassing.
Change the procedure, get the numbers after the push, fine, but let us plug it in on the roll. We can handle it, we do it all the time. What world do these folks think we operate in? IAD in the simulator would be my guess.