I agree with you on most points. Unfortunately as well on the two finger conflict with map applications. 
In theory, I agree with you as well on the one-handed actions. But having bigger and bigger screen sizes makes it already impossible for me to use my phone (at the moment a Xperia 10 III) one-handed, without the fear to drop it. I don’t have small hands. And I don’t think there are many smaller phones on the market.
At the moment I tend to @nephros solution. It seems to be an easy solution and some apps already do it like that, so it isn’t disruptive.
But I would as well accept your “wiggle” solution. I just want some solution. ANd for me it is nota solution, to always scroll to the top, no matter if there is a fast scroll or not.