Once they get working on it, I would think they could get consultation and competitor briefs back within a month. Then have an initial answer within two months of the announcement, and if that answer is a "no" they'd have a good idea of what would need to be changed.

And I don't see a great reason that negotiations should more than triple that amount of time. If they're not budging, make the "no" final. So two months initial, six months max, would be good numbers.

If the company wants to negotiate with everyone in serial... that's their problem.

> and you don't want some of them knowing that everyone else has already said yes, because then they'll hold out to get some last special thing

Wasn't the thesis of this comment line that government regulators are being slow or being a problem? This supports that idea, I think.