ATTENTION: RULE UPDATE!
Even though this tournament allows for eliminating weaker cities and banning overpowered ones, not all remaining cities are equal. In other words, even now, there's a fairly high chance of a successful or unsuccessful city generation. Since the Best-of-3 series has a higher cost for each loss compared to Best-of-5, I believe the rules should be supplemented with one more point to reduce randomness and increase skill level.
Since there are no reports on played matches in the tournament yet, it means either no one has played yet, or only 1-2 games have been played in the tournament. Since the tournament hasn't really started yet, I think a rule update will be acceptable.
The new rule is as follows: during a series of games with an opponent (Best-of-3), you can play with each city no more than once.
That is, if you get city N in the first match, then in the second and third matches (if there is one) with that opponent, you cannot play with city N again.