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 .

This is a duplicate post. Please delete it.