Aah, ok, that explains it. Thanks for the explanation.
A thought: since creating a large set of textures with all combinations of styles is obviously unrealistic, an alternative possibility might be to request the creation of a font texture with a given (user-specified) combination of styles when a typeface is loaded. A specialised typeface like that would of course not be able to take any other styles, but it would solve principally all problems and satisfy all usage scenarios I can think of, as well as actually reduce memory footprint when only a particular style is needed.
The drawback of this solution is of course that colours would need to be part of the requested style.