So here I made my own version of the arena from PopularMMO's and I hope Pat and Jen like it. 

Only truly required mod: Lucky Block Mod 

While you can use this in vanilla you will lose some chest stuff including lucky blocks. So make sure at least have Luckyblocks version 5.1.0 or higher installed. If you want to play this on Multiplayer server then make sure commandblocks are enabled. The arena currently supports 12 players, lucky block-wise.