See my suggestion above - no need to do anything overly complicated, just track the number of times a team has a queue "pop", but does not start the game. If that's over a certain fraction(a very arbitrary 10% in my above post, could be adjusted up or down as appropriate) of the team's total games, they either are penalized, or the games start counting as losses for them.
It's not perfect, but it allows for the occasional ISP hiccup or "oops I just realized I'm in my tanking gear and my PvP gear is in the bank" moment, while still curtailing flagrant abuses.
So the abuse is ok so long as it's not flagrant? I guess in my book forgeting your gear in the bank is on the same page as not bothering to use earthshock or dropping the wrong totems. It's a mistake that should cost you the game and the points.
Even if the rate is the modest 10% of games you still allow people who don't like a map to go from 33% of games on the map they don't like 26% of games played on the map they don't like. That's a significant boost. It's not game breaking but neither is an occasional disconnect. I really think it's a bad idea to tailor solutions to substandard ISP performance.