No, please don't ever try that. Bichirs are quite tamed creatures. Even the aggression of an ornate is nothing compared to that of a piranha. The piranhas will most definitely tear those bichirs apart.
Armored a lot of these questions are answered in the sticky's. If you are really considering piranhas I suggest you read through all of the sticky's in the piranha section. If you don't want to invest the time to read the sections maybe they aren't the right fish for you.