The real question about Attribute or Skill for Empathy is more like "Are you born with it? Does it develop with age? (even if you are in cavern with no one to talk to?)".

So, I don't think it is possible. It's a skill because it takes training. An attribute like Wisdom or Perception should be also used. Everyone could understand how another feel if it's not really hidden behind a good comedy...
And in Dragonlance or Planescape (both D&D products), Sense Motive is the most useful skill (even more useful than any Base Attack bonus!)

SilCore basically breaks it out into two stats: Influence and Psyche. Influence is how good the character is at influencing people - how "well adjusted" they are externally. Psyche represents how "well adjusted" the character is internally. Now, that doesn't necessarily mean a person with a high Psyche score is "good". They can be a raging psychopath and if they're happy about it, they have a high Psyche score. If they're unhappy with being a raging psychopath, they have a low Psyche score. One thing I like about this setup is that it sidesteps the issue of "High empathy=shining and happy" and allows for a wider variety of combinations. For example, you can have the pop starlet that is the rage of the party scene (high Influence) but is a complete emotional wreck (low Psyche). Normally the high Influence score will allow her to keep the low Psyche under wraps but occasionally something will happen and the miserable internal landscape will shine through.

Quote from: SilverlionEmpathy as a stat, how would you feel if there was a mechanical value (word or number) for the Empathy of your character (how they connect to other people, how well the understand both good and bad things going on in others lives, and how well they react to it.)

This has been done in other games. Usually it ties in with "Charisma.

Quote from: SilverlionSee, I'm tempted to put one in something I'm working on, because reputation and contacts are important, but so is instant ability to put oneself into another's shoes and be able to respond favorably in some way (either guiding, or demanding responses from other characters due to that connection)

If they are really important, why don't you stat them out? Rep, Contacts, and Manipulation?