Neat idea, though in general our opinion is that Overview mode is better for trackpad users since you can click on any window. Using Alt+Tab with mouse could get a little strange since you have to keep holding down alt, potentially scroll horizontally, etc.

I agree that alt+tab plus mouse seems like an anti-pattern. You can only see like 4 windows at a time anyway, so you're never more than a few tabs from one you could click on.

With an external mouse (like on a chromebox), it's a pretty natural action. I find myself instinctively pointing. Still, it's not a critical feature.

I guess I expect overview and alt-tab to be more consistent where possible?

Given that alt+tab requires users to know keyboard shortcuts, the alt+tab UI doesn't show all windows on one screen, and it is faster to press tab that use a mouse, I don't think we'll get around to adding this.