Mismatch or not, let's just hope for a good fight. 
I you are looking for a good fight then Conor needs to fight someone who is coming up in the sport of boxing and not someone who is established and at the top of the game. I am sure Manny will school him and if Conor wants his stock to rise in boxing he needs a win and not starting a career with two losses. He is confident that he can win against Manny Pacquiao that is why he will not find other fighters, he is seeing this fight as an opportunity to boost his career.
Everyone is confident before the fight, i am sure Conor McGregor is confident that he can beat Floyd Mayweather if there is a rematch and after that he will think that he can beat the third time around. You cannot fight the best in a sport and expect to win and that is the fact.