I think I’m going to write a script that automagically converts my MIT-licensed fonts into equivalent OFL-licensed ones, so I can post them at openfontlibrary.org. It’ll be a font with ‘OFL’ included in the name and a different copyright notice, but otherwise the same. This approach seems like it wouldn’t be as difficult to manage as a single font with dual licensing; also it is more in the spirit of the OFL license, which is one of those that makes you change the names of derivative works; and it is less likely to give me bug reports that are due to duplicate fonts being installed.
(Anyone could turn one of my MIT-licensed fonts into an OFL-licensed font, anyway, if I am correct. That wouldn’t be true if I were using the GNU copyleft or some such.)