Presumably the ACC would not get tv revenue from road games against non ACC schools. Not sure those rights can be granted.
If it’s actually $0, you’re right, it’s impossible. But I don’t think it’s zero, and I don’t think new members would necessarily get the same deal as other SEC schools until they could contribute all of their media rights. Until then, as the saying goes, we don’t have to outrun the bear, we just have to outrun you.
The ACC would own all of Clemson's media rights unless they were bought out regardless of their conference affiliation. That's why it's such a huge deal. TV/streaming is what's driven expansion - increasing the payout to each school. And they wouldn't add anything without media rights.