From what I know of French history, dueling per se didn't appear until the 16th century when swords got lighter.

What we had before was the "Jugement de Dieu" (God' s Judgment) in which the aggrieved party met its opponent on the field to settle their dispute before God, the will of God being expressed by the gift of victory.

Most times, this judgment was first conducted on horseback with lances and if necessary was prolonged with whatever weapons were chosen, axes, swords, maces...

I fully agree that implementing such a system could be a great addition to the game.