This suggestion is simple
There appears new jobs that are "duel jobs"
they function like normal 2 hour jobs
they have no actual labor point requirement, but when you do the job, you get a duel report back, instead of a regular job report
the duel "job" will give set you up with a random NPC opponent to duel with, carrying a random amount of money based on the the NPC level
this job will use your normal dueling motivation
The enemies you duel is randomed between + or - 5 levels (this can also be decided by some complex formula)
The enemy will have skills in all their dueling skills so that they wont be push overs, probably 2 x level, in every skill
so a level 15 NPC dueler would have
30 shooting, 30 vigor, 30 reflex, 30 toughness, 30 dodge, 30 aim, 30 tactics, 30 appearance, 30 healthpoints
while they will have more total stats then a normal player, in reality since most stats wont be used in a duel anyways, this becomes reduced, not to mention they wont have equips
of course this can be changed as needed