Given the same situation as jiraiya, his kusanagi would be more than sufficient. Orochimaru has shown the ability to move through ground and trees. Manda and his other snakes (unlike jiraiya, he's summoned many snakes in the same scenario) are more than enough to defeat animal path.
1000 oral snakes, hidden shadow snakes and kusanagi possess no chakra and are the perfect weapon for preta. In fact Oro has a lot of deadly jutsu which don't use chakra making it a situation like sm naruto vs paths. In orherwords, he'd do what jiraiya did alot easier. In fact he'd most like escape too since he can be cut in half. Then there's his white snake forms blood which would potentially paralyse all paths.
In short, he'd most likely put up a better fight than jiraiya and still escape.
*this is all without et
The Kusunagi is most likely the only weapon he has that is capable of easily taking out a path. And no, the Animal Path would not be defeated like this. While Manda is fearsome, he is both stubborn and the fact that there are many powerful summons that the Animal Path could produce.
The bird, Rhino, Cerberus, cameleon, Panda, the giant water buffalo, the lobster/crab summon, and the centipede. These summons are pretty much superior to Manda and can provide excellent defenses if the case requires the Animal path to do so.
And, Orochimaru's massive technique, the 1000 oral snakes as you call it, wouldn't be nearly as effective here as you'd think it. Remember the location in which they are fighting, it's not flat land that the snakes can cross over with ease. They are for the most part on small plateforms of land and constantly moving around. That, and Pein is for the most part pretty agile. It's not as if it would be impossible for them to get caught by that jutsu unless Orochimaru is in a ridiculously close range to them.
And, would his white snake form might or might not be able to. All the paths are strictly chakra controlled and corpses, would the poison still effect them? I have my doubts. Not only that, but he can only use such an ability once every two and a half years. If you're using an Orochimaru who can use this jutsu, he is weaker then ever before.
And to counter what could be your next point concerning this, if he does possess one of the Pein's; That is his downfall. His chakra would be horridly distorted by the influx and incoming chakra from Nagato. Nagato could control Orochimaru, now that he is using a body filled with his chakra rods. Something he claimed to be able to do to Naruto when ONE rod was in him.
And, no. He will not Oral Rebirth out of what I just said. Jiraiya's ability to manipulate chakra was wrecked when one rod went in him. Now, imagine rods at nearly every important point of the body that is needed to move the body, getting chakra sent into them.
The only true thing Orochimaru begins to this part is the ability to no die as quickly. He can take out perhaps the Preta Path with Kusunagi. But with the Naraka Path hiding away and reviving each deceased Path, they won't stay down.
Orochimaru would only elongate this battle for he and Jiraiya. Possibly aid him with the taking out of a troublesome path here or there. But they won't be defeating Pein in Amegakure, with both his main body (Nagato) in hiding and the Naraka Path not present on the battlefield as well.
, Tsunade did say that if Orochimaru had changed a bit sooner, then Jiraya may of been alive. I don't know exactly when this change would of occurred, but what if she means when Jiraya went to the rain village? If so, would Oro and J-man be a possible match for pain and his paths? What do you guys think? 
