I think that there would be a little more tactics and less chance with this win condition rule: you have to capture 6 flags AND stay ahead after your opponent play one time.
I mean, you both have 5 flags each, you capture 1, now your opponent has the opportunity to play so he can draw the game capturing a flag.
To do this, he is not allowed to use any of the cards. He can order ONE unit in any section. With this sole unit, he should capture a flag. If he doesn't, you win. If he does, the game continues and it's your normal turn again.
Please let me know what you think about it. Thanks!