Speaking from personal experience, the number of merchants I use which accept zero confirmations for low value transactions is much higher than the number of merchants I use which use Lightning. I suppose this change will force them to adapt.
I don't really have experience with that, I use RBF even when I shouldn't really, so I am used to wait for confirmations.
If the use of LN is that good, that's a good news.
It's also bad news for user who only occasionally spend their Bitcoin on such services. It's unlikely they'll bother use LN wallet or lock their Bitcoin on LN channel when they only make transaction once in a month.
Good point. People will have to wait for at least one confirmation if they go on-chain.
If I'd do that I would at least consider using a custodian LN wallet (like blue wallet). Not a perfect solution, but it does the job once in a while.