I don't pretend to know all of the details, but I think it would require a hardfork.

I think zkrollups would be a fantastic way to increase demand for blockspace and steal marketshare from Ethereum.

Like it or not, Ethereum's shitcoin casino is generating a ton of demand for blockspace. And there are some legitimate things on ETH, too (like the ability to borrow against your (wrapped, unfortunately) BTC and use stablecoins).