Since most operations happen within the same window, zooming in and out constantly is needed to see how changes to a glyph look in a word context. I think I would have to scroll a lot less if the zoom function placed whatever glyph I’ve selected at the center of the screen. So, if I’d want to change the r, I could just select it and zoom in.
Which zoom function are you talking about? Keyboard shortcuts? Alt-scrolling? Pinch-zooming?
If you want to zoom a special area, why not simple use drag-zooming? (Hold down space&cmd, drag a rectangle?) It is pretty much exactly what you are asking for, just without sacrificing the selection, faster, and more flexible.
I’d find it handy for cmd+/- to focus on the selection too. Also, when zooming in on parts of glyphs way outside the metrics box, for the viewport to allow scrolling to all parts of an outline. (I know the workarounds but don’t find them massively practical.)