A tournament where you can win about 500k gold and lose a city worth maybe a thousand times more and then not even speaking about the military units you can lose... hmm.. This tournament needs alot more balancing I guess..
I'm not entering a tournament where the only thing I can win is useless gold wich I have enough allraidy.
But I do have some Ideas:
1) maybe a tournament mode where you will win when you have distroyed the entire city wall (with max 5 battle rams.) This way, more people are willing to play in such a tournament. A tournament where you can lose a city will not get alot of players.
2) The tournament randomly choose a city where you will need to distroy the city wall. This way a challenger will not automaticly go for the smallest town wich is alot of easier to delevel the wall.
3) After tournament is accepted, both player will have 1day to prepare their armies, upgrade citywall a bit further and maybe send some diplomatic units ahead to gain information about the armies and citywall level at that moment.
4) 2 tournament modes. 1 for prestige players and 1 for normal players. A prestige player will have a big advantage over normal player because they can instantly rebuild their citywall. Also saboteurs would not work against prestige players.
5) While you are in the tournament you can not recive trades wich support your towns with resources. They will return home.
6) Also other players can't attack the siege camp and can't reinforce the players. They will also return home with the message ''cannot attack/reinforce player X because this player is fighting in a 1vs1 tournament.
7) Tournament has a deadline. They have to distroy the other players citywall within a specific time (maybe 14days?) The player who lost the most citywall upgrades will lose when this date is over.
8) The gold as a buy-in for the tournament. Then maybe put in advanged resources as reward that the other player needs to accept (or find another tournament wich is more tempting to accept) Winner takes all (gold buy-in + the accepted resources)
9) A new building where you can view, accept challenges. At every upgrade you can put in a bigger reward. --> building lvl 1: max 100 advanged resources, lvl 2: max 250 advanged resources.. etc etc..
But a 1vs1 tournament would need alot more thinking and work than this.