Flipster. I have to say it was not a federal pacific breaker that made the box or wire melt it was probably poor workmanship and perhaps a person who was not licensed or properly trained. Regardless of plastic or metal there likely would have been trouble. Plastic is absolutely safe and fine for most residential installations when installed by someone who actually cares about what they are doing. ( As you seem to) If you plan to be in business for the long haul I don't think you will find enough people to work for who would rather pay for serious overkill rather than a safe and code compliant job. I find that many people think with their checkbook. You simply can't compete with someone using lower cost materials that install faster and easier with a savings in labor.
PS I hate to go into a basement and see a panel full of FPE breakers as well!
PPS about 15 years ago an apartment building burned near where I lived. The cause: a nail through a peice of Armored cable. The neutral was broken and the nail completed the circuit to the armor. Bring on a nice arc and poof FIRE! I wonder if an AFCI would have prevented this.
