How about the ability to specify customisable formatting buttons? Each button could be implemented by specifying a name, icon, start/end braces and precedence, where the selected text already has formatting. By selecting the target text and clicking the button it would surround the text with the delimiters and be hilighted in the bare text panel to distinguish it, much the same as now.
Perhaps implement it as an optional second row of buttons? How about multiple rows, each of which could be imported/exported as a config file?
