You can customize it with CSS. Make it borderless and transparent, then put over any fancy sprite and you have your magic done.
The problem with using that to constantly change a spritefont is that there is no insertion point. Even now that I had made an insertion point sprite It cannot select text or be moved by mouse. I cannot find a workaround to force it to do these things with sprites, but a plugin or feature that allows you to easily edit each moving and non-moving part of a textbox like you would a sprite would be absolutely perfect. Obviously plugins and features take a while so right now I'm trying to simulate it. What do you suggest I do to add text selection and insertion point and text movement to this? Any help would be great!