You’d be amazed at how hard it is to find information about the yogh. First, I’ve managed to learn that Unicode 4.0 Latin Extended B does indeed have both an upper and a lower case yogh, a yogh is that not an ezh. Take a look, if your browser supports Unicode 4.0 characters: an uppercase yogh Ȝ or U+021C and a lower case yogh ȝ or U+021D. And there are even Mac OS X fonts that support yogh as part of the Unicode character set (I particularly like Junicode). That’s the good news.
The problem is that the only word processor (versus text editor) for Mac OS X that supports the complete Unicode character set, and by “supports” I mean I can use Insert from the Character Palette, or hex encode the character, is Nisus Writer Express. Microsoft Word X does not, since the character is a Unicode character; neither MarinerWrite nor AppleWorks 6.x support Unicode only characters. The problem with Nisus Writer Express is that it doesn’t support footnotes, and the more esoteric formatting dissertations require. Mellel looks promising though, and I have hopes for true Unicode support in Microsoft Word 11. My ultimate plan is to create a custom keyboard layout, so I can easily access the characters I need. But I’m still going to check out LaTex.