This isn’t common goal for developers. And furthermore problem solving isn’t easy. Actionscript code doesn’t give access to available classes at runtime. So only trick I can image is parsing swf file by itself and get class names. Crazy implementation? Yes, it is. :-) But no coding here because flash decompilers written in actionscript already exist.

Swfassist:

Subject with loading font isn't new but some its part weren’t still described. Or I missed them and had to walk through debugging nightmare.

So target application is text/image editors on flash that gives user option to be unique and change font style of his label. And the problem is the font as other graphic content has some weight. Including fonts to application affect on user traffic and experience, because user has to wait longer. And here usually comes idea don’t load all fonts with application and load them only when user require it.