So .. what's the problem ... if you want to surrender but no one else does, drop the game. You have stated your intentions that you want to quit. A loss is a loss, and they get to continue playing with an AI.
I would oppose this notion. Many times 1 guy is loosing heavily but the other 3 are doing great. So him dropping and the AI picking up can be really bad for your team.
Have a look at how the others are doing first, in 4v4 one guy getting huge losses does not necessarily mean the end of the game. If 3 guys don't want to surrender it might mean they see from their perspective they have a fighting chance.