I actually find that a little worrisome. I've always felt that romantic subplots shouldn't be rushed or forced to manifest as quickly as possible, but need some time to develop organically. And the handling of such wasn't exactly one of the strong points in ATLA: the relationships tended to be ignored for long stretches of time, then advance in huge leaps largely offscreen.
They're really pushing a Mako/Korra ship early and hard.
I'm fine with him not secretly being anyone we know, and discovering his identity not being a major plot point. But to some degree we do need to eventually find out something about who he is, because that's an important factor in understanding why he does what he does. Unless he's just evil for evil's sake, one presumes that there's something in his backstory to indicate his reasons for starting this insurrection, even if it's just cynical desire for power. (To use your own example, in V for Vendetta, while we never see V's face or learn his name, we do learn about his past and his reasons for hating the government.)
I kinda hope they go the V for Vendetta route and have Amon's identity never revealed, or at least have him be someone we never met before. His importance to the story should be what he does, not who he is behind the mask.
Given that Amon wears a mask, it would be interesting if it were to turn out that he wasn't any one person, but actually multiple people hiding behind the same identity. Not a man but a symbol. Every time that they think that they've killed him, he re-emerges unharmed... but it's actually another man behind the mask, taking his place.
But I don't really care what Amon turns out to be behind that mask, as long as it turns out to be compelling storytelling.