A much smaller chance, since Arrow has not been known to mess around with other realities like The Flash, is that he’s the Earth-2 Floyd Lawton.
The questions now is, just how the hell are we going to see Floyd Lawton again?
Well, one possible answer that could easily be used to explain a lot of changes to the Arrow-verse now, is Flashpoint.
Barry Allen came into contact with him during his time on Earth-2, as he worked for the Central City Police Department and wasn’t actually a bad guy there.