He would have to sacrifice someone living to bring back someone dead. Are we to assume because he is a "good guy" that maybe he used enemy ninja as sacrifices?
It still doesn't seem like a technique that a "good guy" would develop. Everyone, even the villains, think it's an "unforgiveable" technique. Again, not what you'd expect from a good guy. And who's genetic material did he have/who did he bring back?
And if his version was not perfected as Kabuto and others have claimed, how was it different?
The only reason I can think of that he'd create Edo Tensei is maybe to talk to the 1st, but again he'd have to kill someone to do it.
What do you all think?
I think the goal was to develop a jutsu that could revive the dead in a way similar to Rinne Tensei.
In the theme of the show - if one could resurrect the dead, one could put a stop to the cycle of attack and retaliation. Edo Tensei was, likely, Tobirama's attempt to find a solution to Nagato's question (much like Infinite Tsukuyomi is an attempt by Madara/Obito to answer it).
Perhaps the Zetsu were supposed to be a crucial part of facilitating such a jutsu - but the idea scrapped by Tobirama after he could not resolve issues with the jutsu that put it in conflict with ethical/moral tenets. Perhaps because he could not overcome the fact that the user of the jutsu had control over other individuals. Perhaps because the resurrected were quite ashen and dead-looking. Likely a combination of all the above.
That said - the abilities of the jutsu make it an effective weapon if need be. And that's possibly what led to it being labeled a forbidden jutsu - as we can see in the case of Kabuto, one can potentially wield a great number of revived ninja of great power and unlimited chakra (curious to know where that comes from). It's simply too convenient and too powerful for one person (let alone a few) to be running around with.
... But it seems it's become something of a Pandora's Box.
I can see the revival of the Uzumaki clan being a priority of the allied nations following the war... restoring their sealing techniques (that, ironically, were once feared) would be quite useful in making sure that the dead stay that way. Given that much of the war was made possible by Kabuto and Edo Tensei - it would stand to reason that many clans would be interested in making sure that their passed members can rest knowing that they will not be able to be used in such a manner (provided the Uzumaki develop some kind of seal that is incredibly difficult to crack open).
Though I may be getting a bit ahead of myself, there.
