It might be possible to hack something using jscallbacks.js, the problem is to make the label persistent, for that you must store them somewhere on the server side, and that makes things much more complicated. If you can use/abuse the device&user mode it would be the best option, there is an user event broadcasted when a user logs in, and a couple of astdb entries stored, you could replicate those to make fop2 change labels when those events are fired.
