I know two
Cecilia's and I've never heard them called anything but
Cecilia. Although it's a long name, it seems to be an exception to the whole long-names-need-nicknames thing. I don't think you have to worry much about it. Cici, for instance, could be a cute occasional nickname but it doesn't necessarily have to stick.
Judith is kind of different though. With
Judith comes the expected nickname
Judy, whereas
Cecilia doesn't have an obvious nickname. I think a
Judith would be called
Judy more often than a
Cecilia called Cici or
Celia or something, you know?
Anyway, while I dislike
Cecilia, I think
Judith Cecilia is beautiful. I prefer it to
Miriam Judith and
Cecilia Rose, although those are both nice as well. :)