doesn't work that way. Even if you could get a 100% efficient air to air intercooler (which you can't), it could only ever cool the air to ambient temperature.
A Water to air intercooler can theoretically exceed 100% efficiency, but there is little point in cooling the inlet charge a degree or two before you heat it up anyway.

The intercooler is only useful after the compressor, because as you compress air you heat it also - regardless of the conductive heating also transferred to the inlet charge. You want to cool it down as much as possible before it enters the engine.

You are right about the potential of an intercooler to explode if filled with a combustible mixture - one little backfire and it's a goner. But that doesn't stop the speedboat guys from doin it! Although I don't think CAMS would take too kindly to it...and I don't like the idea of things exploding and burning under my bonnet either!