That doesn't even remotely answer the question. Where's the implication that they're exact replicas of the original? Replicating appearance=/=perfect copy.
It's only superficial. Obv in FF7 it was just Jenova shapeshifted, and in AC it's negative lifestream. He doesn't have organs, the biological systems, none of that.
I'm pretty sure that's what Masamune meant about it being an exact replica: It looks just like his original body. Appearance is usually the primary topic on the table when you're dealing with shapeshifters.
Dacon said:
What does fixing his body have to do with his downfall? He rebuilt himself better and stronger than Jenova ffs.
Because if he'd simply gotten business done then he wouldn't have gone out like a chump. Same reason dicking around with Cloud most of the game was fucking retarded.
And I'm still not seeing cause to believe that his original body with his will inhabiting it is necessarily any more powerful than JENOVA's body under his control with his spirit and will inhabiting it. Yes, he put up a better fight than the parts of JENOVA you fight throughout the game, but, then, JENOVA-Death put up a better fight than Life -- and Life better than Birth.
Later battles are typically harder than earlier battles. That's just how it goes.
Of course, Seph never intended for AVALANCHE to lose those earlier battles either, so it's pretty much beside the point either way. He can't be assumed to have meant business until the JENOVA-Synthesis battle, and it's not like the final battles were all that much harder.
I said as well, Jenova+Kadaj (Dark Lifestream) was needed.
You said he was composed of negative Lifestream, the implication being that you were leaving out the physical material component of the equation.
Shikamaru said:
If just a litre of Jenova cells is all he needed for Reunion AC and the Silverhaired men wouldn't have happened. What does Reno taking away from the Northern Crater accomplish? Nothing. He can and has controlled Jenova from the other side of the world.
As Mako explained, he was unable to control the cells until his spirit came in contact with them again. That's the whole point. If he were able to control them otherwise, he would have just had them move around under his command the same way he did in FFVII.