Personally I often mix and match skills with attributes as I see fit to keep things interesting. This is a typical example of that. If you want to stick with Intimidate(Strength) I would give a bunch of Fortune dice. But I would say that Guile(Fellowship) would be a pretty good choice as well. Granted, it's a bit outside what guile is usually used for, but it's still using an underhanded method to get what you want through social interaction.

You could always change the base Attribute for a needed skill. For example, if you think the player should be Intimidating the NPC then let him roll Intimidate, but using his Fellowship instead of Strength, or Intelligence if he is using his intellect to Intimidate. For the actual roll, this means that a character with a Strength of 3, Fellowship of 4 and no ranks in Intimidate, would roll 4 Attribute dice and no Expertise dice. The same character with 1 rank in Intimidate would roll 4 Attribute dice and 1 Expertise die. Plus any white dice as seen fit.

This game is meant to be flexible and rules adapted to fit the situation. This is not against the rules but actually encouraged by the game - just look at many of the Action cards, lots of them use different Attributes for skills that are given in the rule book.

I think there's a talent that lets you use intelligence (I think it was) for intimidate checks. Seems like a good choice for a character who wants to do this sort of thing.
That talent, and a bunch of others actions/talents etc, would loose some of their usefullness if the skills and attributes are mixed and matched to the players liking to often.
Why purchase a talent when you can get the benifit it offers for free? So I'm quite restrictive when it comes to mixing and matching skills-characteristics, even if I allow it sometimes.

Both a blackmail and hostage situation could probably be in similar ways though using any of the social skills. To make it more interesting you could use a tracker and make several rolls, both for the player character(s) and their foes. Then you can encourage the use of different skills and reward good roleplaying with white dice during the encounter.

Guile could be especially appropriate in a hostage situation especially if you're actually bluffing, i.e. you do not want to destroy the object, but you need to convince your opponent that the threat is actually real and hope that they do not call your bluff.

But most social skills (and some other skills) can probably be used bu clever players (leadership to "take the offensive" socially, intimidate to make threats/be the "bad cop" in the situation, charm to come off as the "good cop" etc). Even coordination could be used to toss the object and catch it at the last second to show the foes that you mean it.

You can use that special card that does everything their isn't an action card for.

Do a Intimidate(Willpower), its Willpower what your really testing. You not trying to be scary with your body, your trying to be scary with your mind.