So here is the idea, short and sweet:

• Allow users with the following permission node: <spectate.radius> to issue this command /spec radius
  - This displays all players with in the radius of X blocks and displays them in the GUI.
• Another feature that you could implement is permission nodes for certain radius's. For example <spectate.radius.30> would only allow to be 30 in /spec radius .

Edit by pgmann:

• /spec mode radius command;
• config option spectateradius: 30 or something like that.

I have decided not to add this feature for the foreseeable future, as I don't think there's a big demand for it and it has limited uses.
Closing as won't fix.

Thank you, I closed the duplicate issue for you. We'll add it when we get a chance :)

Okay thanks a bunch!