Well, if Ron Brown says it's a bad idea, then it's probably a bad idea. I'm just glad it worked for me and my motobecane engine is not in 1,000,000 pieces, or a molten puddle of aluminum on the floor.
If you aren't worried about the cylinder, I would go ahead and try the ice method. The only thing I would be afraid of is cracking the cylinder because of the low temperature brittleness and the ice becomnig non-fluid. If that happens then it would still help get the piston out of there.
As for the risk of explosion, this is why they put safety valves in steam-powered espresso makers - heating water in a confined space isn't exactly safe. I was fairly confident that something would give way before it exploded.
Is there any way you could plug up your exhaust port? If it uses a bolt on flange, you could bolt on a piece of plate steel, or if it's the kind with the big nut that screws into the port, maybe you could find something round that would fit in under the nut. If your transfer ports are uncovered, that's a different story.
Did you try the heating and quenching method? I may be corrected but it really seems like that would work the best. If you just heat it, I'm sure the piston would expand even more into the cylinder walls. It takes a lot of heat to raise the temperature of that cylinder, considering the mass of it and the fact that it's designed to conduct heat away from the cylinder. If you torch it for a really long time, it could make a real difference. I found the best way was to set the torch up so that it's blowing diagonally down the side of the cylinder, and you can see a swirling of the gas all around the cylinder wall. Then you can switch sides to heat it more evenly. You could also heat the cylinder from the outside, and hopefully get more heat to the cylinder and less to the piston.
Good luck. After all this it should feel really good when the piston does come out.