I recenlty made up thing that meant 2 bulbs could work from the one slot, so you could get a good bulb that wasnt causing a fault as the power source the other bulb would get its power from that, here the engine management light supplies power to the airbag light, both come on and go out at the same time:

I caused the fire when i left the metal legs on the airbag bulb, the two shorted out and caused the mini fire, just cut off the bulbs legs and tape or blu tack the bulb in place
Its dodgy as hell, and it can set your instrument cluster on fire, but its nice to know it can be done, as for the LED lights in the multiplexed instrument clusters if you had a fine enough soldering iron you might be able to put two small wires to send power to another LED, cut the tracks supplying power to the offending LED and they might work, i dont know how it would cope with the extra current draw but the older bulb cluster worked fine.