I would be helpful to be able to set the default font size in many different areas as well. I like the default font size of 10, but I find that many of my users prefer to have a size of 12, especially in the sheets. With dual monitors, and higher resolution screens (and us older users!) being able to set the default size of new rows would be a big time saver.
On forms, reports and dashboards, I am also finding myself changing the font size to make things easier to read. Even if it was a global setting, I can see many advantages to setting the font size, and then adjusting where needed, rather than the other way around.