>>718040104
two problems
the game is not designed for an arena, dwarfs get spooked when they see the enemies so no viewers.
second is: capturing enemies for it (cage traps) feels like cheating but there are no other way. Personally i would have preferred having the option of imprisoning downed enemies after you already defeated them (like in rim).

You can still have fun however, either by making a huge mess and dropping enemies to fight against themselves, or a better pragmatic option is using arena as practical training for your army.
i always overcompensated and sent much more dwarfs than needed to defeat something but you could make it more personal and send one or two per round. Maybe if you feeling really adventurous send them against themselves.
on that topic I've once had a dwarf who fought all the time and ended up killing >15 dwarfs before i retired the fort. When you have enough of them its not a real issue.