Mercy system for AFK victims in Promotion Series

tl;dr: If a player leaves a ranked game, summoners on that player's team who are in a promotion series should not receive a loss for that game.

Let me begin by saying that I understand leavers are part of the game, that Leaver Buster does a pretty good job of preventing serial offenders, and that over a large sample size of games, leaver activity will actually work out to the advantage of the honorable player. However, there is one part of the game where a very small sample size is given an outsize importance: promotion series. In a series, one AFK can undo days or weeks of work, and adds additional misery to games that are already extremely stressful to begin with.

I know I am not the first person to suggest that the victims of AFK's should be given some mercy, but I think that this particular case is worth considering. Climbing the ladder is hard enough without leavers making it worse. I know this is quite rare, but I have even seen players leave a game to intentionally ruin another summoner's series. Since poor etiquette and negativity seem to be an inevitable part of LoL, I propose that this small counter measure be put in place for the cases with the largest impact.

Since a feature like this is prone to abuse, I suggest the following limits and controls be placed on it:

-- For a leaver's team mates who are in promos, the game counts as neither a win nor a loss (i.e. for the purposes of the series, it never happened) -- The leaver still receives a loss if they are in a series (obviously) -- If the leaver is part of a duo queue, their duo partner is not eligible for mercy -- The leaver must have been inactive for a certain minimum threshold** -- No mercy will be given for LP or MMR calculations, as these will work themselves out over a large number of games

** I'm not exactly sure what this threshold should be or how it could be measured. I also don't think this control is totally necessary, but it's worth investigating.