Dave Crossland informs about new tool: https://github.com/twardoch/ttfdiet
"ttfdiet (TTF DIacritics Encoding Tool) applies a “diet” to a .ttf font: it modernizes the way in which glyphs for precomposed Unicode characters are stored in a TrueType-flavored OpenType font, and reduces the font's file size." [from README.md]

I installed Behdad Esfahbod's FontTools https://github.com/behdad/fonttools/archive/master.zip and wrote diet.bat file:

python c:\ttfdiet.py %1
pause

- be sure Python (2.6 or higher) is installed and added to the PATH
- "c:\ttfdiet.py" it is where file ttfdiet.py is stored
- there is no output font file name, so ttfdiet will create ttf file, with .diet added, in the path where input font file is stored
- "pause" let me to see what will happen

It works perfectly. Fonts were tested in BabelPad and FireFox 32.0.3 (winXP sp3). See FireFox:

I don't care the file is smaller, important is that errors are clearly visible (I marked some with red circles). I belive font will be better when "diet-proof" or "diet-ready".