As the title says, remove merc mode from battlegrounds.
If you choose to play horde, you deal with the long queues.
Merc mode is being abused and used as a means to troll. Almost every BG has horde on the alliance team that throw the game for laughs, and even announce it in chat. If you call them out on it and try to get everyone to win, they report you afk to get you kicked.
You chose the overpopulated faction, you should not be allowed to skip the line for BG only to ruin the experience for others.