personal champ pool (know more than one champ per role before playing ranked)

(please move to the right spot if gameplay isn't the right place for this post)

ok, so my little rant is based on my last game, in which we had a teemo jungle because of the fact that his jungling champ(he had tryndamere hovered) got banned. I just really hate when somebody does this because it really ruins the game for the rest of the team. the whole "oh they banned X champ and that was the only champ I know of for this role, looks like I'll play Y champ that isn't even suited for this role now." If your only champ gets banned either have a back up or ask to switch with somebody else.