Extend the ability to spectate to dead players even if everyone is dead. At game end still allow clicking the spectator button to renter game (spectating should be the default and opting out of spectator mode should be the thing you click, but that is another issue).
What this would look like is: I’m in a game, I think my opponents may be collaborating but I’m not sure enough to file a report. With their final moves the player going out third makes it obvious. My certainty has gone up drastically but it’s the final seconds of the game. I’m dead, but I got second so in the current system I can’t file an in game report or look at the battle log. New system I am able to “spectate” the static screen of the conquered map, look at the battle log and report players or even continue to emote or communicate with allied players. Problem solved.