I think that the first Tournaments should definitely be trial runs and held on standard maps from Heroes 3: The Shadow of Death. Also, the time limit for completing them should be extended. I suggest using any standard map from The Shadow of Death and giving players 1 month to complete it. I think this would be a good start. Natasha, it's your turn.

The beginning was actually quite good! I didn't manage to play because I didn't have enough time. It's just that I knew who I was playing against and wasn't very happy with the way things were going, and on the map, a lot depended on the behavior of the computer. That's why I didn't have the patience to replay it.

A longer time limit could increase the number of participants, but it's not a guarantee. Waiting a month, and then finding out that you can count the number of saves on one hand... It's better to keep it as it is - 10 days for a tournament.
Reducing the time limit as an experiment is a good idea!
Arena tournaments are, of course, more difficult; they require not only tactical skills but also an understanding of strategy. Standard victory conditions (kill everyone, take all the castles, etc.) might be easier to understand, but such a game is less interesting.