I would like to help but I don't have a lot of time the coming two months.
However I can help a bit anyway. A while ago the author of a Perl module
which converts oldstyle TeX diacritics to Unicode made a plug on the XeTeX
mailing list:

Since I have used XeLaTeX exclusively for nearly a decade I havent tried it
but the code looks OK.


onsdag 12 augusti 2015 skrev Galen Buttitta <
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> I would like to make the Index Unicode-compatible for ease of searching,
> but redoing the entire 300+-page document in XeTeX or XeLaTeX or whatever
> would take me a considerable amount of time. Therefore, I am asking for
> help.
> Would any of you be willing to convert a section or few? I'm told that
> there's ways to include multiple documents in one document, so I could use
> some help on that as well (and changing the page orientation for certain
> pages, which would make it easier to display the phonologies of, for
> instance, the Caucasian protolanguages).
> If you're interested, please shoot me a message.
> Thank you.