I ran spectator mode today whilst I made lunch for my kids. At the point in time that I went to spectator mode, the game at hand was only 5v5… but by the time I returned to the game, it had upsized to 8v7.
Was I taking that 16th slot, and preventing someone else from coming in to play and even the teams? Do spectators count against the 16 player limit?
If so, and spectators add to the 16 sum-total, I think it would be best if it did not (if possible).
I like to use words that lie on the periphery of the english vernacular.
It’s always been this way in just about any game. A slot is a slot, the only time you won’t take up a slot as a spectator is if you’re on a game that has TV servers and you’re in it.
The more important thing they need to work out is why there is no first person spectator mode. Also the game needs game recording of some sort.
Free look and first person view spectator mode are a must. And I was really hoping SD had added these features by now.
Back to the subject in question: A spectator will always take a slot. It’d only make sense. Imagine if I was a spectator, and at the moment someone is connecting (loading the map) I join a team, making it 8v8. That person that’s now connecting is unable to join any teams and is forced to stay in spectator mode.
If anything, spectator slots would be rather neat. Some games do this. But again, that’d only be great if there was a free look, first person look and recording feature. 
I’m going to cross my fingers that some day in the near future, SD will implement spectating without taking up a player slot.
Bring on the no slot spectator free look demo feature. I would be happy with demo recording.
Rarely to happen as you take up bandwidth. Most server companies would cross your plans too as you rent 16 server slots when you order a brink server.
And that’s why I said I’d cross my fingers, not hold my breath. 
Some players I have noticed will wait as a spectator a looooooong time so they can get on a team that is currently full. Kinda funny.