It would be really nice if you can develop a site or even the main theme to achieve 100 scores on everything in the Lighthouse / Wed.dev dashboard. I believe it will be more suitable for a site rather than the core.
I can clearly see a benefit in these scores when other factors like content quality, engagement signals and backlinks are playing a factor. Having these scores does impact rankings if everything else is good.
I think Accessibility scores does impact rankings as well as speed the way Google measures it.
Yes, it will be the new thing that everyone would want. I am an SEO, I know the purpose of these and how they will be reflected in the SERPs. I can tell that you will really have new customers – people that know more about these scores and they are not few.
What I am saying is that there would be a market for SEOs for that matter, I just don’t want to say more about it, if you can understand. But I do predict a huge demand for these particular scores in the near feature. You can competitively do it before everyone else does.