huh?!?
wait.. you couldnt ignite propane with steelwool, glow-plug and even a filament? cant be! either it was *that* cold that it didnt glow yet, or there was no propane (and/or air) at that place..
a filament will be 3600° before melting, get it to 1000° red-hot and you will ignite *any* fuel-air-mix that is remotely burnable!
for your new idea: sounds good, but.. how about a solar cell? how about installing that cell pointing to the sky? you need heat for ignition, therefore electrical power, which comes from the laser. a one-watt laser would kill the cell, and would still barely provide enough power for heat-generation, if it wouldnt kill the cell. you could TEC-cool the solar cell of course! oh, and widen the beam before impact on that poor cell! ;-)
manuel