I've made a mob arena for noobstown as the old mob arena was great fun, so i hope foob could add it.

If foob agrees ill send a schematic file for it, it's exactly 128 blocks tall so i suggest you place it at layer 63 to prevent the top or bottom being cut off.

Here's a pic of it.

Spectator area's round the side, mobs spawn on red circles and players spawn on the blue circle.
And yes the lobby is in the same place as spectators.

The arena has some redstone underneath it, this was a failed attempt at making it work without plugins, it doesn't do anything.

This looks very good It would be good if Joe could consider it.