For those who are working with datasets they'd like eventually to link up with Pleiades, we created the Barrington Atlas ID scheme. I've just posted some more tools for helping you determine the BAtlas IDs to go with your existing geographic names or other information.
There's now a draft "Barrington Atlas Index with Identifiers". In PDF (watch out: 7.2 MB) it looks like:
It's also available in a 1.0 MB zip-compressed HTML version, with somewhat semantic class attributes on spans that could be used to parse out different themes ahead of an attempt to match it to a names list:
And of course there is already the home-brewed XML format we distributed the original IDs in (last release tar-gzipped archive):
Share and enjoy!