Not that we know of. You have to play through Mercenary to get to Veteran. And since that starts around level 40, I suspect you might find it a challenge with characters who haven't at least reached the beginning of Act III on Mercenary.
To the Righteous belong the fruits of violent victory. The rest of us will have to settle for warm friends, warm lovers, and a wink from a quietly supportive universe.
Why not try to change things on your end to make things more difficult. Do something like choosing fewer party members or not using healing spells or something like that.