(I don't want to hear about how crazy I am to want that! :)
Focus-follows-mouse is also known as point-to-focus, pointer focus, and (in some implementations) sloppy focus. [Add other terms that will make this more searchable!] X-mouse
I've been coming back to this question periodically for about 10 years and I finally found a simple solution: AutoRaise https://github.com/sbmpost/AutoRaise
By default it enables focus-follows-mouse AND autoraise. You can delay the autoraise with a config option.
It also has what they call "warp" function that centers the mouse pointer in a window when you Command-Tab to the window. I never knew I needed this until I tried it, but once I tried it, I can't live without it!