you really can build a planted tank around pracitcally anything if you're creative enough... I've had good luck adding about 3/4" to 1" of Estes natural #1 gravel on top of any plant substrate to keep the plants from getting uprooted. also, strategically placed slate can work wonders. A couple of interesting fish that I've seen kept with discus in biotope settings are Satanoperca leucosticta (previously Geo. jurupari), which although big, is pretty passive, biotodoma cupido (dwarf eartheater--rapps usually has them available), tigrinus cats, lima SN's , even FW barracudas (Acestrorynchus spp.) the eartheaters can be tough on plants, but if you stick with hardy and robust species like swords and Anubias, they don't usually cause too many difficulties. Good luck setting up the tank--
Mike