I would personally strongly advise against this. You see the high beam side of the headlight housing have a different reflector (Or lens on a OEM headlight) which is how the housing defines it's beam pattern. So even a lower wattage bulb (Say 50W halogen) installed, the beam that the high beam side of the housing throws off will still cause glare and will be offensive to oncoming drivers. Also I don't know what state you are from, but it is illegal in a lot of states to have 4 headlights on while on low beam. All states allow for vehicles to have the vehicles low beams on and the fog lights (if equipped) on while on low beam, but most do not allow for vehicles to have 4 headlights on while on low beams.
I would also recommend that you find what is wrong with the high beams currently that is causing them not to work. A good place to start would be to check at the 9005 (High Beam) headlight connector with a DMM or test light and see if your getting any voltage. If you are getting voltage at the headlight connectors, check the filament within the bulbs and see if they are burned out. If you are NOT getting any voltage, it could very well be your headlight switch or dimmer/multi-function switch. I would strongly recommend finding out what is causing them not to work before altering anything else.