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Schwartz's Luxury does this, as Im sure others do. Instead of being able to pick between regular(roman) and italic, in illustrator you get a drop down menu with the options 'diamond' 'gold' and 'platnum.'
I have read the FL manual and figured out how to actually do this, but I know that doing anything unconventional in the computer world often ends up creating usability problems in some way. For example, perhaps doing this would make the fonts invisible to certain programs, because they don't understand the format.
If anybody has fooled around with this, I would love some pointers on how to make sure the fonts always work properly.