As I spent a fair bit of time in the Arena yesterday, I noticed that some of the areas seemed a little wasted. There are multiple areas with tefus in, and two with Trepors in. There is also an area with just two Clackers in it.
I was thinking that maybe we could introduce the tougher creatures to the arena, and re-organise it a bit. Make one room with Tefusangs, one room with Trepors, one room with Marfusangs, another room with Ulbernauts, the dlayo room, one room with Robust Trepors and Robust Tefusangs, and another room with Maulbernauts and Grendols. Put all clackers in the intermediary areas, increase the number of rats in the staircase areas, leave rogues as they are. You could also add Thunderclackers to the mix somewhere.