https://community.bistudio.com/wiki/Description.ext#respawnOnStart

respawnOnStart = -1;//Dont respawn on start. Don't run respawn script on start.

I don't know where you put the spectator code, but i recommend you put it in onPlayerRespawn.sqf in this case to make things easier.

Added 1 minute later:

On second thought, this might complicate things even more.

I don't know if the loadout respawn menu will ever run if you put it like that, unconfirmed on my side though, so should be worth a try.