Hey Kamikaze, I'm new to this site as well, but I can do a little more than just solder stuff. So let's see if I can help you.
Sure, the pneumatic cannons are more powerful, but you want to make combustion; I can appreciate that.
So you want to have some remote button of some sort that will ignite the gas in your combustion chamber. So you need an arc of some sort, just like what's in the BBQ behind the house. If we want to do this with the piezo-electric idea, you'd likely be looking at using the switch to start a motor that would load then release a spring to smack the piezo crystal. So this is still using the ignitor from the BBQ, but with an unnecessary step in there.
I think what you are looking for would be something strictly electronic, without the physical motion, right? If that's the case, I think something with a capacitor discharging would do the job. Let me get out the old electronics kit and see what I can get going here.