Great project! Web designers need absolute control over charset and font size (load), kerning, word and letter spacing, etc. Support for OpenType features [1] would be a dearly needed addition. Editing/tweaking of glyph shapes [2] would make this tool really into an in-browser font editor.

[1] http://en.wikipedia.org/wiki/List_of_typographic_features [2] Check nodebox.github.io/opentype.js/ (https://hackertimes.com/item?id=6459778)