are you planing to use multiple fonts on the screen at the same time?
yes.
My current implementation allows to change the color of the text on the fly. I'm mostly concerned with bold/italics and size changes which, at least in my current implementation, require a new font texture.
I also use a 1 file font, but it isnt to hard to produce a font list from multiple files.
I'm trying to avoid that

. It would be annoying to have to change textures in the middle of drawing the text. Even if it was optimized to draw all the characters of a string that require one texture, then change and draw the rest. Thats still possibly hundreds of texture changes every frame.

Right now I'm thinking of making the font textures smaller (maybe 512x512) and just using OpenGL to stretch them to the size I need. It won't look as nice, but it would work.