I just got the following e-mail:
We’re drafting a proposal to add as many remaining unsupported phonetic and orthographic symbols to Unicode as we can justify. I thought you might have come across things you’d like to have encoded. You seem like the kind of person who might have stashed away notes on things like that.
We’re not interested in idiosyncratic inventions that never spread beyond their authors, or obsolete systems that scholars don’t bother to use even when citing sources that do use them, but sometimes Unicode doesn’t support things in fairly widespread use, such as superscript variants of IPA characters, subscripts made superscript to avoid descenders, letters with a swash for velarization, and informal IPA letters or substitutions. Or if you know of a really neat symbol that should be available but isn’t, and can send published documentation, we should be able to include it.
So this is your chance: if you’ve got ideas on the subject, put ’em in the thread and they will be seen by someone who can do something about it.