[dread78645]

What's the difference, from a theological perspective, between "Before Christ" and "Before the Common Era" when BOTH are based on the same event reference?

No, they're different.
Jesus was born either around 6 BCE or 6 CE.
The earlier date comes from Matthew -- Jesus was born 2 years before Herod the Great died in 4BCE. The later date is from Luke -- Jesus was born during the tax census when Rome dismissed Herod Archelaus (Herod's son) and Judea became a province under direct Roman control.

So we have the choice of a Christ "Before Christ" or the "year of the Lord" (AD) before he was born. Neither one makes sense.

The principle of least effort (POLE) dictates that you leave the dates alone and recognize that the starting point has nothing to do with the birth of Christ.

... use BAB for Before the Atom Bomb and AAB for After the Atom Bomb ...

I can go with that -- although my personal favorite is AA and PA (ante Alexander and post Alexander)

[ZULU]

I guess you are an Alexander the Great man.

I kind of liked Genghis Khan - he had a way with Muslims I kind of admire.