That's fair! just seeing about getting some speculation, ideas going in case we come up with something interesting

Otherwise, i like were your going with that custom challenges idea. Although little nits like changing 'team' to 'guild' or 'custom games' to 'Challenges & Custom Games' come to mind.
I think the challenges could possibly work out pretty good as it'd provide some of the more prominent players of the game a means to create content for the community. I don't consider myself a very prominent player as most of my time in the game is spent making realms and the like.
If you manage to give said prominent players means to send out challenges and the like, in a way that isn't time consuming, you could possibly see some really cool returns from it.
Though tournaments keep coming to mind, even if it was just a means of setting up a series of games and having a 'reputation' reward by the end of it that's covered by all parties who enter (you use reputation to enter a tourney and possibly leave with all of the reputation that gets put in the pot)
Challenges could also work as custom games were 1 demigod is able to create 1 challenge at a time, and is able to replace it when they want *otherwise a limit to how many times it's played like realms could be another good buffer as fall back* and players could simply occupy the lobby until it is full and ready for play.
Alternatively, players could possibly enter Async versions of these challenges and play them that way.
A choice to have challenges that include other players, or are simply player vs AI would be another good opton to have for PVE players who might want to try a challenge solo or with a friend. Another variant could be 1 player vs 4 who has a buff (like a tricky objective that all players have to beat, while he/she defends it)
Objectives on top of all of this......could breath some life in their.
I suppose whats most important to me is:
-Challenges that demigods/gods can create for players
-the ability to have PVP challenges as well as solo/coop PVE challenges
This could possibly be more robust and player retaining then realms if done right. From a user content creator and player perspective.