hm, the bloom shader is already a fake for a real HDR effect. making a fake bloom would mean a fake of a fake. what exactly do you need from the bloom effect?
-the smoothness of colours? (no idea)
-the glow around edges? (look for the glow shaders in the wiki)
-the lighting/contrast? (set your sun value to a rather high value, so the screen will become much brighter without losing its contrast in the dark areas)

sorry i'm not really of any help, i know.