Just make it so players can vote to abandon game within the first 2 minutes of the game (only if no first blood has been taken). This will allow games where players never connected to be forfeited with no LP penalty. Make it so the team that utilizes this function all gets hit with a dodge penalty.
Small detail: voting can only start at 1:15. This is too allow players who have client/internet issues in the beginning some leeway to rejoin the game. It also allows more time for players to walk into lane/jungle camp. There is almost (less invade) no reason for teams to forfeit before this time mark.
Small detail 2: This option is only available for games in which most of the players are below diamond level. Level 1 plays are more significant in higher elo play and therefore the potential use for abuse is higher.
Any options to allow forfeitures after this mark will be too susceptible to abuse and should be not implemented. However, nothing significant happens in the first 2 minutes (less an invade) and therefore creates no harm to allow implementation of this system.
Moreover, if you are dealing with a disconnect/afk issues well into the game - that's just bad luck. RIOT should not have a system to account for this, as the potential use for abuse would be close to 100%. The only way a system like this can happen is if RIOT allows loss forgiven for the losing team but forces the disconnecting/afk player to drop an entire division/tier. Harsh punishments would discourage players from "taking one for the team (abuse)". This punishment is most likely too harsh in most incidents, and therefore should not be implemented. If ya'll wish, the League community can voice their opinion and agree that AFK/disconnects (FOR ANY REASON) should be punished with heavy LP loss and/or division/tier drop. This would happen even if the reason for your disconnect is because Comcast went down or your loved ones were sent to the hospital. Before voicing an opinion on this, think what you would want if something unexpected happened to you that was out of your control. Point: someone needs to take the punishment for the loss, it can't just be completely forgiven. So either someone loses LP equal to all 5 members, or everyone loses LP equally.