font.letterSpacing should add the same space to all letters

The doc states :

Letter spacing changes the default spacing between individual letters in the font. A value of 100 will keep the spacing unchanged; a value of 200 will enlarge the spacing after a character by the width of the character itself.

Which is exactly what the property i doing, but is, in my opinion, perfectly useless for the designer. As the spacing after each character depends on the width of the character itself, it leads to an unevenly-spaced, difficult-to-read text. See the attached screenshot, with a letter spacing of 200

A much more desirable behavior would be to add the same amount of space to all the characters. This amount could be, for example, relative to the capital N or capital M. Thus, a letter spacing of 200 would enlarge the spacing after each character by the width of the letter N.