mondengel:

Thinking about how Tobirama went into such detail about the “Uchiha Curse”, I had a thought: what if he intended the Uchiha to be the last line of defense for the village?

That seems like an obvious statement – he had assigned them as the police inside Konoha, of course they would defend the village if anyone got that far.  But I think the thought behind it was more complicated than that.  Tobirama basically said he’d given them a job they were suited to when pressed about it.   The Uchiha can copy any jutsu, have massive chakra and can predict an enemies movements.  This makes them excellent shinobi all-around, but does indeed make them specially suited to policing and apprehending unruly ninja.  But Tobirama didn’t mention this anywhere in his explanation – he kept bringing up the Curse.

The Curse of Hatred: Uchiha suppressing intense emotions to the point that when they are released (usually in times of great turmoil) they develop the sharingan (if they don’t have it, they get it, if they have it it evolves) and their power increases exponentially, short and long-term.  With the unfortunate side effect of often making them tend to lean toward rabidly insane.  See: Madara, Obito, Sasuke.  

Tobirama has studied this over his entire life.  Seen first-hand as the sharingan has evolved on the battlefield in enemies he’s fought, or watched it bloom in the eyes of the survivors as they glare and retreat.  He watched Madara’s steady decent into a madman that abandoned his village as his eyes grew more and more powerful – reduced from the kind, family oriented man Hashirama first met to a deluded lunatic who would attack and torture members of his own clan in his unquenchable hate.  All because his beloved brother Izuna was killed.  In this light, every single Uchiha is a ticking time-bomb.

Keeping them in the village put them in an environment where they
weren’t being stressed out so much and alleviated this danger.  Canon (or at least word-of-god)
says there weren’t a lot of Uchiha with the sharingan at the time of the
massacre, which supports this.  Certainly Tobirama would have seen the Uchiha safe inside Konoha, using their strengths to maintain order better than anyone else, and noted the uptick in them keeping their sanity intact.  Making their in-village position official was logical.  The Uchiha themselves were safer and happier overall, and everyone was safer from them. 

But that Curse would have also been a tempting contingency. 

Any enemy of the village who made it to the village would be confronted by an entire clan of fire-breathing berserkers where they expected competent, but pampered policemen.

By Tobirama’s reign alone, it would have been an entire generation since the Uchiha were on the battlefield properly.  Sure, there would be one or two out on teams, but not as a large group.  Not as brothers and fathers, and sisters and mothers, and cousins and uncles side by side as an army, red eyes ever-watching, ever evolving as their kin died beside them.  Probably no one had killed an Uchiha loved one and lived to tell about the resulting carnage in decades.  No one would have been wary of the instant backlash anymore. See: Obito.  The shinobi that cut Kakashi’s eye was entirely unwary of Obito and died quickly for it.  Tobirama could even have used the newly formed Anbu to wipe out information about the Uchiha outside the village specifically to cause enemies to be unwary when killing an Uchiha’s loved one.  There probably aren’t any surviving records in enemy hands about nearby Uchiha suddenly turning savage and twice as strong if you killed one of them, or how sometimes one would start screaming as the body fell and take a suicide run into the nearest group of enemies and decimate dozens before they were brought down. 

I think the Uchiha Curse of Hatred wasn’t something Tobirama could get rid of and knew it, but it was something he could direct and use.  And did.

If anyone got past the vanguard and defenses comprised of the Senju and other assorted clans of Konoha, they would be expecting weaker shinobi, or, at-best, think they understood how the sharingan worked (copies jutsu and tracks movement – lol, easy) and rush in half-cocked.  And start killing people.  And the Uchiha would inevitably rise like the many heads of the Hydra – cut one down and another twice as strong and three times as vicious is coming at you from the left.  

I think Tobirama intended the Uchiha to be an integrated part of the village.  They supposed to love it and the people in it deeply. 
Recall: Tobirama expressed surprise and said he couldn’t believe the clan was on the brink of extinction when he was told Sasuke was the last.  He does mention concern about Madara’s adherents within the clan, but clearly the clan as a whole was meant to be safe and stable in the village.

His failure was in thinking too much about the system he was developing and not enough about the people.  How people resenting the police and how the logic of putting the clan in charge of the prison, beside the prison would isolate them socially and physically, and (most importantly), how his successors would interpret his warnings and intentions.  Danzo (and Hiruzen) seem to have listened too closely to Tobiramas words about the strength and danger of the Uchiha and not enough on their suitability as protectors.  Penning them into an even more remote district post-Kyuubi and cutting them off from everyone else would have messed that plan for the Curse up; effectively reversing the founding of the village for the Uchiha. 

At their end, the Uchiha’s love was turned inward to themselves; exactly as it had been before.