You know...when you think about it...that's not a bad idea to give the winner their default health/shields back.
For one thing, it would give more of an incentive for saberists to enter into more duels, rather than getting stuck in a group of 5 or 6 with everyone twirling and slashing like crazy. I don't care what you say...it's near impossible to keep an eye on every player and offer a counter-move. It turns into a slashing match, where you score a lucky hit...and then you get sabered in the back by the player you never knew was there. That's fair enough if you enjoy that sort of thing, but more thoughtful duels seem to work best between 2 or 3 people at a time.
If the winner of a duel could be assured that they could regain their default health/shields...then they would have, as you say, a fighting chance against a gunner waiting for the duel to end to kill the winner.
So that would negate the possibility of people going into duel mode and coming straight back out again with full health/shields...only the winner of the duel would be given that bonus, forcing the saberists to fight.