Why not that for Gorgo? Sounds like a lot like Thermopylae.And how about a Hoplite buff, too?
How about... +5 Combat Strength versus other unique units? Or, +5 Combat Strength versus units of civilizations with a stronger army. Just ideas.
I think of Pericles as the city-state leader, so I don't necessarily see the need for Gorgo to get those bonuses.