Okay, so after reading all of these comments I came to my conclusion that this /spectate command is probably not going to be added because:
-Helpers are apparently 27/4 in every FFA game ever and can spectate all players at the exact same time, so there is no need for it.
-The server would look more like mineplex.
-It has been suggested before.
-Getting killed 10x to record a hacker is apparently just as easy and takes the same time as spectating the hacker for gathering evidence.
-People would abuse it because they would know the map better and find all easter eggs and "secret places" easier.
-There isn't enough room for players that want to spectate, but there is enough room for players that want to play, even though the FFA servers are almost never full.
Am I considered weird for losing faith in some people of this forum right now?