AFK kiss of death solution
Let someone else pick up where your AFK left off.
Just that. If someone AFKs for more than a set period of time (say three minutes) then let someone ELSE load their game and continue with their champ. In game mode select, we'd need the option to "AFK Fill".
This would help AFKs be less of the kiss of death that they are now.
The player subbing in for the leaver could be of slightly higher ELO to compensate for his champ being dead in the water for 3 minutes, or get some kind of in game gold bonus.
The sub would still be screwed 9 times out of 10, since his predecessor was probably a toxic feeder, and his team will still lose, so he could get an IP bonus or loot.
The AFK player would still get his punishment