"Would", used for speculation or inference

Question

Scene 1

Katniss Everdeen: President Snow. What an honor.

President Snow: My dear, I think we can make this so much simpler. If we agree not to lie to each other, what do you think?

Katniss Everdeen: Yes, I think that would save time.

President Snow: Sit down, please.

Scene 2

Johanna Mason: How do we know the wire's not gonna burn up?

Beetee: Because I invented it. I assure you, it won't burn up. [they all look at each other for a moment]

Johanna Mason: Well, it's better than hunting them down.

Katniss Everdeen: Yeah, why not? If it fails, no harm done anyway, right?

Peeta Mellark: Alright, I say we try it.

Finnick Odair: So what can we do to help?

Beetee: Keep me alive for the next six hours. That would be extremely helpful.

--The Hunger Games: Catching Fire

I think these two would are used for speculation or inference and no conditionals are implied here.

When used this way, is it a less definite form of will? PEU¹ and Advanced Grammar in Use say little on this particular usage of would.

Can you please elaborate on this?

^{1. PEU = Michael Swan's, Practical English Usage.}

Answer 1

Your instincts are on target: in these cases would is being used in the same sense as will, but also expresses some doubt. That would be Y said in response to some X can be read here more or less as if X is true, then Y.

In scene one, there's some doubt over whether or not they'll both tell the truth. Also, in American English, would often sounds a bit more polite than will, and this is (I presume) a formal conversation between Katniss and the President.

In scene two, the doubt is over whether Beetee will be kept alive. I'm not familiar with the program, so I can't tell if Beetee is being sarcastic or not here. If so, the sarcasm implies that the question was stupid or unnecessary.

In both scenes, the person using would (Katniss or Beetee) is the one having doubts, though not necessarily the only one.