The point of the arena was to make it possible for players who wanted to duel for fame and cash could travel to the Imperial City and fight anytime they wanted, or not go there if they wanted.
The new Challenge system forces fights on players who may not want to fight yet. It also loots cash from them, too. Imagine waking up to find 20 people have challenged you, your fame has dropped 300 points and your cash has been looted down to zero. That is what will happen as the game continues the way it is set up now.
We should have the option to turn challenge on or off. Watching this game degrade into the typical beatdown games we find elsewhere, where the top players/bullies have fame of 3000 while everyone else is farmed for fame and cash makes no sense.