Since this thread is about missing glyphs, may I ask how can one contribute by creating missing glyphs? By creating and sending you a ttf containing only the missing glyphs? The GNU FreeFont project uses scripts to convert images containing the font characters to a ttf file, which makes sense for non bitmap fonts emulating pixels since it is easier to draw a character in a drawing program than to draw a pixelized character using lines in a traditional font authoring program.
I have already used online pixelized font creation sites such as bitfontmaker2
http://www.pentacom.jp/pentacom/bitfontmaker2/
which lets you import and export font data as a json file and also let you import ttfs, but supports only latin characters. I also have used Fontstruct
which seems to let you drawn any character for any unicode block and also let you easily "fork" someone elses font and copy paste characters from one font to another, but does not let you import ttfs and there is no keyboard shortcut for copy pasting wich makes copying characters a tedious process