yeah, the reason why they want naruto in the first place was to extract the kyuubi, but i dont think that having naruto transformed into a fox was part of the plan... and i do believe that madara employed pain to do the task coz madara knew naruto can easily break down and coz pain is rinnegan user, he can thereby use all the jutsu in the world just, in case, the fox might come forth... but none in the manga or even the anime have i ever seen that naruto was to be hurt so much as it did with the other bijuu... that is in deed a reason for me to believe that naruto's bijuu is very special to madara...

too bad, nagato was so weak tho or else, the kyuubi should be in the hands of the akatsuki now...
no prob...

that too is possible as we all know nagato is in a different level... even nagato's tech that earned him the nick, yellow flash, involves a seal so its safe to say nagato was a sealing specialist...no argument there...