I think there should be an in-game button to vote to unrank the current game. There are often situations where this is desired (ie: someone was AFK for the first minute of the game, both teams don't want to play the ladder/TMM map they got, someone has to go, the wrong game settings were chosen by mistake, the game is too laggy, someone crashed, etc). Every live non-AFK player would have to opt-in to cancelling/unranking the game for that to happen. The functionality would be similar to what the draw button does, but it would actually unrank the game rather than make it a draw, and it would not require the votes of AFK players.
