I think it would be reasonable to consider moving a company making large changes like that into some kind of probationary state, and automatically adjust the weights it has in the index as a result.

This is true, and it's why index trackers exist, in order to diversify risk across the market so an investor is not excessively exposed to that happening for particular stocks. The market then re-prices that stock. As an index fund investor you are outsourcing your discretion to other market participants.

However the market hasn't priced these new stocks at all, the existence of index trackers is being exploited to force prices on enough buyers to make the prices stick. This is the wrong way around. It's market manipulation. It's using the behaviour of index funds to influence prices, decoupling those prices to at least some extent from the discretion of market participants.

Let the market price the stock, then the index trackers can buy in, this is exactly why these rules exist, and why it's a travesty that the NASDAQ is waiving them.