Alright, from personal experience, you shouldn’t put players in spectators during 16 rounds 
(not even 2 rounds imo)
But it depends on the length of the rounds I guess. If the rounds are long and you need to keep that spectate mechanic because the gameplay cannot be designed otherwise, I’d suggest either :
- Enabling and Disabling Matchmaking dynamically using the
Round Settings Device* - Giving an alternate thing to do while they wait for the current rounds to end (UI or ig minigame / training…)
It’s a good thing that you did your own round system, so congrats on that 
I’m assuming that you already know the method to trigger things when a player joins the game in Verse, then when a player joins the game (AND gets spawned in), you can just look at the current game state (your previous 1 to 5 bullet points) and act accordingly.
If I understand correctly, basically the only thing you want to do here is send them to spectator if the rounds are currently running right ? (assuming the Game Start Area is indeed the default spawn location, also assuming we don’t show the voting UI for them, that’s how I’d do it)
In order to do so, you’ll want to either kill them when they spawn, or change your island settings Join In Progress parameter to be set on Spectate by default, which means you’re basically reversing the problem (coz you’ll now need to spawn players if the rounds are not currently running)
You could also do like I did in Minigames Box PVP and add a spectate box in the Lobby area that the players need to intentionally go inside if that fits your needs better
On a side note, I’m also curious of what you’re doing if players don’t pick a team 