Ah. I had downloaded and played a very tiny bit with some font-editing software a couple months ago. I put it on the back burner, but give me the weekend to play, and I might have some thoughts for you.
The software is TypeLight, from
http://www.cr8software.net/typelight.html. You can use it to add glyphs to an existing font, and it might be an easy thing to add the logo to your Symbola subset. I had only tried out a couple of glyphs, and the software is really easy to use.
Something for you to consider, anyway...
EDITED TO ADD: I forgot to mention, TypeLite is Freeware! Also, the Pro edition is available on a trial basis, limits you to (I think) 50 or 52 characters.