Youtube, for one: https://techcrunch.com/2011/10/30/the-entire-1-65b-acquisiti...
Android as well, if I'm remembering correctly.
They don't necessarily need to complete the acquisition in a week, just get the broad details negotiated and agreed to. Given the GP's bankruptcy example, if they thought it was worth the risk the acquirer can extend a bare minimum amount of credit to keep the company alive while they do the rest of due diligence and finish the acquisition, folding it into a breakup fee.
Virtually every single bank failure that happens results in an M&A that is negotiated over a weekend.
Most recently Credit Suisse collapsed in March. UBS bought it on Monday, March 19, after negotiations began on Friday, March 16. UBS offered a price that was 60% lower than the Friday closing price. The deal was accepted.
I know this is already a stressed straw man in the first place but M&A are aren't a short simple process anyway. Adding some oversight isn't going to change that.
Yes there are tradeoffs to more regulation vs total anarchy/free market. That doesn't mean they're not worth it. "Good" is not the enemy of "perfect" and all.