Hmm, this has proven to be quite the topic.Okay. Because I have multiple thesis on the subject of how the objects Nagato controls are not alive besides the fact that it has already been confirmed that they are not alive and their chakra paths are only active because Nagato fuels them. He literally controls the entire theme of it. They may have blood, they might have organs, but they simply don’t work like a living creature (or summon) does. Also confirmed. The summons don’t even have contracts. Nagato takes them like someone takes booty in jail. Snatched. The only reason ”they“ operate as such as to not be destroyed beyond repair because Nagato finding a suitable replacement is harder than just outsmarting his opponents and beating them like he knows he is capable of.
Aside from that, with the fact that Kisame is heavily nerfed and the centipede being considered “alive”, I still do not see how Kisame would deal with its sheer size and raw power. He cannot sap the chakra, I am not an expert on Sameheda so I am not sure what it’s capabilities are as far as it’s non-sentient form (assuming its sentient form is banned). However, if we allow Kisame’s pseudo-beast form which I don’t think we are considering it going by what Itachi would accept in his village, I think it would be a more decent battle considering his raw strength in that form. He also has some streamlined techs that aren’t village-busters but lethal nonetheless.
Actually, the defeat of the paths and summons do have them behaving like normal summons with living bodies, even if that is clearly not the case. Consider how Divine Path was defeated by R.G. as a normal person would be. If it was like a puppet, then Nagato could have continued with its limbs intact.
The repair arguement implies a practical defeat, imo. Like, the stipulations of the thread itself. If any path would be beaten beyond repair, that's as good as being defeated by his normal choice.
As for replacements, he has a storage unit of them, based on Summoning Path. So i think that may be a more sentimental link to Jiraiya. It doesn't apply to his animals, though.
The shark form is allowed, but a huge water construct is restricted. I think Itachi would be okay with a small pool up to the size of the centipede itself. You?